diff --git a/gcc/elna-diagnostic.cc b/gcc/elna-diagnostic.cc
index ec1b8b5..fda487f 100644
--- a/gcc/elna-diagnostic.cc
+++ b/gcc/elna-diagnostic.cc
@@ -40,10 +40,18 @@ namespace gcc
         {
             return "pointer";
         }
-        else if (is_array_type(type))
+        else if (TREE_CODE(type) == ARRAY_TYPE)
         {
             return "array";
         }
+        else if (TREE_CODE(type) == RECORD_TYPE)
+        {
+            return "record";
+        }
+        else if (TREE_CODE(type) == UNION_TYPE)
+        {
+            return "union";
+        }
         else
         {
             return "<<unknown-type>>";
diff --git a/gcc/elna-generic.cc b/gcc/elna-generic.cc
index b8a2cb2..1f0c3d7 100644
--- a/gcc/elna-generic.cc
+++ b/gcc/elna-generic.cc
@@ -20,7 +20,7 @@ namespace gcc
         this->symbol_map = symbol_table;
     }
 
-    void generic_visitor::visit(source::call_statement *statement)
+    void generic_visitor::visit(source::call_expression *statement)
     {
         auto symbol = this->symbol_map->lookup(statement->name());
 
@@ -87,7 +87,8 @@ namespace gcc
         }
         else if (symbol)
         {
-            tree fndecl_type = build_function_type(void_type_node, TYPE_ARG_TYPES(symbol->payload));
+            tree return_type = TREE_TYPE(TREE_TYPE(symbol->payload));
+            tree fndecl_type = build_function_type(return_type, TYPE_ARG_TYPES(symbol->payload));
             tree printf_fn = build1(ADDR_EXPR, build_pointer_type(fndecl_type), symbol->payload);
 
             std::vector<tree> arguments(statement->arguments().size());
@@ -97,10 +98,17 @@ namespace gcc
                 arguments[i] = this->current_expression;
             }
             tree stmt = build_call_array_loc(get_location(&statement->position()),
-                    void_type_node, printf_fn, arguments.size(), arguments.data());
+                    return_type, printf_fn, arguments.size(), arguments.data());
 
-            append_to_statement_list(stmt, &this->current_statements);
-            this->current_expression = NULL_TREE;
+            if (return_type == void_type_node)
+            {
+                append_to_statement_list(stmt, &this->current_statements);
+                this->current_expression = NULL_TREE;
+            }
+            else
+            {
+                this->current_expression = stmt;
+            }
         }
         else
         {
@@ -126,9 +134,6 @@ namespace gcc
         tree resdecl = build_decl(UNKNOWN_LOCATION, RESULT_DECL, NULL_TREE, integer_type_node);
         DECL_CONTEXT(resdecl) = this->main_fndecl;
         DECL_RESULT(this->main_fndecl) = resdecl;
-        tree set_result = build2(INIT_EXPR, void_type_node, DECL_RESULT(main_fndecl),
-                build_int_cst_type(integer_type_node, 0));
-        tree return_stmt = build1(RETURN_EXPR, void_type_node, set_result);
 
         enter_scope();
 
@@ -140,6 +145,9 @@ namespace gcc
         {
             body_statement->accept(this);
         }
+        tree set_result = build2(INIT_EXPR, void_type_node, DECL_RESULT(main_fndecl),
+                build_int_cst_type(integer_type_node, 0));
+        tree return_stmt = build1(RETURN_EXPR, void_type_node, set_result);
         append_to_statement_list(return_stmt, &this->current_statements);
         tree_symbol_mapping mapping = leave_scope();
 
@@ -163,15 +171,17 @@ namespace gcc
         {
             parameter_types[i] = build_type(definition->parameters.at(i)->type());
         }
-        tree declaration_type = build_function_type_array(void_type_node,
+        tree return_type = definition->return_type() == nullptr
+            ? void_type_node
+            : build_type(*definition->return_type());
+        tree declaration_type = build_function_type_array(return_type,
                 definition->parameters.size(), parameter_types.data());
         this->main_fndecl = build_fn_decl(definition->identifier().c_str(), declaration_type);
         this->symbol_map->enter(definition->identifier(), source::make_info(this->main_fndecl));
 
         if (definition->body() != nullptr)
         {
-            tree resdecl = build_decl(UNKNOWN_LOCATION, RESULT_DECL,
-                    NULL_TREE, TREE_TYPE(TREE_TYPE(this->main_fndecl)));
+            tree resdecl = build_decl(UNKNOWN_LOCATION, RESULT_DECL, NULL_TREE, return_type);
             DECL_CONTEXT(resdecl) = this->main_fndecl;
             DECL_RESULT(this->main_fndecl) = resdecl;
 
@@ -454,7 +464,7 @@ namespace gcc
         location_t definition_location = get_location(&definition->position());
         tree definition_tree = build_decl(definition_location, TYPE_DECL,
                 get_identifier(definition->identifier().c_str()), tree_type);
-        auto result = this->symbol_map->enter(definition->identifier(), source::make_info(definition_tree));
+        auto result = this->symbol_map->enter(definition->identifier(), source::make_info(tree_type));
 
         if (result)
         {
@@ -477,31 +487,11 @@ namespace gcc
     {
         if (source::basic_type_expression *basic_type = type.is_basic())
         {
-            if (basic_type->base_name() == "Int")
-            {
-                return integer_type_node;
-            }
-            else if (basic_type->base_name() == "Bool")
-            {
-                return boolean_type_node;
-            }
-            else if (basic_type->base_name() == "Float")
-            {
-                return double_type_node;
-            }
-            else if (basic_type->base_name() == "Char")
-            {
-                return elna_char_type_node;
-            }
-            else if (basic_type->base_name() == "String")
-            {
-                return elna_string_type_node;
-            }
             auto symbol = this->symbol_map->lookup(basic_type->base_name());
 
-            if (symbol)
+            if (symbol && TYPE_P(symbol->payload))
             {
-                return TREE_TYPE(symbol->payload);
+                return symbol->payload;
             }
             error_at(get_location(&basic_type->position()),
                     "type '%s' not declared", basic_type->base_name().c_str());
@@ -844,5 +834,26 @@ namespace gcc
 
         this->current_expression = NULL_TREE;
     }
+
+    void generic_visitor::visit(source::expression_statement *statement)
+    {
+        statement->body().accept(this);
+    }
+
+    void generic_visitor::visit(source::return_statement *statement)
+    {
+        source::expression *return_expression = statement->return_expression();
+
+        if (return_expression == nullptr)
+        {
+            return;
+        }
+        return_expression->accept(this);
+
+        tree set_result = build2(INIT_EXPR, void_type_node, DECL_RESULT(main_fndecl),
+                this->current_expression);
+        tree return_stmt = build1(RETURN_EXPR, void_type_node, set_result);
+        append_to_statement_list(return_stmt, &this->current_statements);
+    }
 }
 }
diff --git a/gcc/elna-tree.cc b/gcc/elna-tree.cc
index 6cac5ee..a4c3156 100644
--- a/gcc/elna-tree.cc
+++ b/gcc/elna-tree.cc
@@ -28,12 +28,6 @@ namespace gcc
             && TYPE_MAIN_VARIANT(TREE_TYPE(type)) == char_type_node;
     }
 
-    bool is_array_type(tree type)
-    {
-        gcc_assert(TYPE_P(type));
-        return TREE_CODE(type) == ARRAY_TYPE;
-    }
-
     tree tree_chain_base::head()
     {
         return first;
@@ -76,7 +70,16 @@ namespace gcc
 
     std::shared_ptr<elna::source::symbol_table<tree>> builtin_symbol_table()
     {
-        return std::make_shared<elna::source::symbol_table<tree>>();
+        std::shared_ptr<elna::source::symbol_table<tree>> initial_table =
+            std::make_shared<elna::source::symbol_table<tree>>();
+
+        initial_table->enter("Int", source::make_info(integer_type_node));
+        initial_table->enter("Bool", source::make_info(boolean_type_node));
+        initial_table->enter("Float", source::make_info(double_type_node));
+        initial_table->enter("Char", source::make_info(elna_char_type_node));
+        initial_table->enter("String", source::make_info(elna_string_type_node));
+
+        return initial_table;
     }
 }
 }
diff --git a/gcc/elna1.cc b/gcc/elna1.cc
index 4d36b6f..51d76e7 100644
--- a/gcc/elna1.cc
+++ b/gcc/elna1.cc
@@ -100,7 +100,7 @@ static void elna_parse_file(const char *filename)
     }
     else
     {
-        elna::gcc::generic_visitor generic_visitor;
+        elna::gcc::generic_visitor generic_visitor{ elna::gcc::builtin_symbol_table() };
 
         generic_visitor.visit(driver.tree.get());
     }
diff --git a/include/elna/gcc/elna-generic.h b/include/elna/gcc/elna-generic.h
index 905d376..ea280dd 100644
--- a/include/elna/gcc/elna-generic.h
+++ b/include/elna/gcc/elna-generic.h
@@ -39,7 +39,7 @@ namespace gcc
 
         void visit(source::program *program) override;
         void visit(source::procedure_definition *definition) override;
-        void visit(source::call_statement *statement) override;
+        void visit(source::call_expression *statement) override;
         void visit(source::number_literal<std::int32_t> *literal) override;
         void visit(source::number_literal<double> *literal) override;
         void visit(source::number_literal<bool> *boolean) override;
@@ -57,6 +57,8 @@ namespace gcc
         void visit(source::assign_statement *statement) override;
         void visit(source::if_statement *statement) override;
         void visit(source::while_statement *statement) override;
+        void visit(source::expression_statement *statement) override;
+        void visit(source::return_statement *statement) override;
     };
 }
 }
diff --git a/include/elna/gcc/elna-tree.h b/include/elna/gcc/elna-tree.h
index 64f5e31..59d9c88 100644
--- a/include/elna/gcc/elna-tree.h
+++ b/include/elna/gcc/elna-tree.h
@@ -6,6 +6,8 @@
 #include "tree.h"
 #include "tree.h"
 
+#include "elna/source/symbol.h"
+
 enum elna_tree_index
 {
     ELNA_TI_CHAR_TYPE,
@@ -25,7 +27,6 @@ namespace gcc
     void init_ttree();
     bool is_pointer_type(tree type);
     bool is_string_type(tree type);
-    bool is_array_type(tree type);
 
     class tree_chain_base
     {
@@ -58,6 +59,6 @@ namespace gcc
         tree block();
     };
 
-    std::shared_ptr<elna::source::symbol_table<tree>> builtin_symbol_table();
+    std::shared_ptr<source::symbol_table<tree>> builtin_symbol_table();
 }
 }
diff --git a/include/elna/source/ast.h b/include/elna/source/ast.h
index d363aa9..3c2c62a 100644
--- a/include/elna/source/ast.h
+++ b/include/elna/source/ast.h
@@ -39,11 +39,13 @@ namespace source
     class constant_definition;
     class procedure_definition;
     class type_definition;
-    class call_statement;
+    class call_expression;
     class compound_statement;
     class assign_statement;
     class if_statement;
     class while_statement;
+    class return_statement;
+    class expression_statement;
     class block;
     class program;
     class binary_expression;
@@ -71,11 +73,13 @@ namespace source
         virtual void visit(constant_definition *) = 0;
         virtual void visit(procedure_definition *) = 0;
         virtual void visit(type_definition *) = 0;
-        virtual void visit(call_statement *) = 0;
+        virtual void visit(call_expression *) = 0;
+        virtual void visit(expression_statement *) = 0;
         virtual void visit(compound_statement *) = 0;
         virtual void visit(assign_statement *) = 0;
         virtual void visit(if_statement *) = 0;
         virtual void visit(while_statement *) = 0;
+        virtual void visit(return_statement *) = 0;
         virtual void visit(block *) = 0;
         virtual void visit(program *) = 0;
         virtual void visit(binary_expression *) = 0;
@@ -105,11 +109,13 @@ namespace source
         virtual void visit(constant_definition *definition) override;
         virtual void visit(procedure_definition *definition) override;
         virtual void visit(type_definition *definition) override;
-        virtual void visit(call_statement *statement) override;
+        virtual void visit(call_expression *statement) override;
+        virtual void visit(expression_statement *statement) override;
         virtual void visit(compound_statement *statement) override;
         virtual void visit(assign_statement *statement) override;
         virtual void visit(if_statement *) override;
         virtual void visit(while_statement *) override;
+        virtual void visit(return_statement *) override;
         virtual void visit(block *block) override;
         virtual void visit(program *program) override;
         virtual void visit(binary_expression *expression) override;
@@ -403,6 +409,7 @@ namespace source
      */
     class procedure_definition : public definition
     {
+        type_expression *m_return_type{ nullptr };
         block *m_body{ nullptr };
 
     public:
@@ -411,12 +418,16 @@ namespace source
         /**
          * \param position Source code position.
          * \param identifier Procedure name.
+         * \param parameters Procedure formal parameters.
+         * \param return_type Return type if any.
          * \param body Procedure body.
          */
         procedure_definition(const struct position position, const std::string& identifier,
-                block *body = nullptr);
+                std::vector<variable_declaration *>&& parameters,
+                type_expression *return_type = nullptr, block *body = nullptr);
         virtual void accept(parser_visitor *visitor) override;
 
+        type_expression *return_type();
         block *body();
 
         virtual ~procedure_definition() override;
@@ -439,7 +450,7 @@ namespace source
     /**
      * Call statement.
      */
-    class call_statement : public statement
+    class call_expression : public expression
     {
         std::string m_name;
         std::vector<expression *> m_arguments;
@@ -449,16 +460,29 @@ namespace source
          * \param position Source code position.
          * \param name Callable's name.
          */
-        call_statement(const struct position position, const std::string& name);
+        call_expression(const struct position position, const std::string& name);
         virtual void accept(parser_visitor *visitor) override;
 
         std::string& name();
         std::vector<expression *>& arguments();
 
-        virtual ~call_statement() override;
+        virtual ~call_expression() override;
     };
 
-    class compound_statement : public statement
+    class expression_statement : public statement
+    {
+        expression *m_body;
+
+    public:
+        expression_statement(const struct position position, expression *body);
+        virtual void accept(parser_visitor *visitor) override;
+
+        expression& body();
+
+        virtual ~expression_statement() override;
+    };
+
+    class compound_statement : public node
     {
     public:
         std::vector<statement *> statements;
@@ -469,6 +493,19 @@ namespace source
         virtual ~compound_statement() override;
     };
 
+    class return_statement : public statement
+    {
+        expression *m_return_expression{ nullptr };
+
+    public:
+        return_statement(const struct position position, expression *return_expression);
+        virtual void accept(parser_visitor *visitor) override;
+
+        expression *return_expression();
+
+        virtual ~return_statement() override;
+    };
+
     class designator_expression : public expression
     {
     public:
diff --git a/source/ast.cc b/source/ast.cc
index 07d6837..820c553 100644
--- a/source/ast.cc
+++ b/source/ast.cc
@@ -33,7 +33,7 @@ namespace source
         definition->body().accept(this);
     }
 
-    void empty_visitor::visit(call_statement *statement)
+    void empty_visitor::visit(call_expression *statement)
     {
         for (auto& argument : statement->arguments())
         {
@@ -41,6 +41,11 @@ namespace source
         }
     }
 
+    void empty_visitor::visit(expression_statement *statement)
+    {
+        statement->body().accept(this);
+    }
+
     void empty_visitor::visit(compound_statement *statement)
     {
         for (const auto nested_statement : statement->statements)
@@ -66,6 +71,16 @@ namespace source
         statement->body().accept(this);
     }
 
+    void empty_visitor::visit(return_statement *statement)
+    {
+        expression *return_expression = statement->return_expression();
+
+        if (return_expression != nullptr)
+        {
+            return_expression->accept(this);
+        }
+    }
+
     void empty_visitor::visit(block *block)
     {
         for (const auto definition : block->value_definitions)
@@ -433,8 +448,8 @@ namespace source
     }
 
     procedure_definition::procedure_definition(const struct position position, const std::string& identifier,
-            block *body)
-        : definition(position, identifier), m_body(body)
+            std::vector<variable_declaration *>&& parameters, type_expression *return_type, block *body)
+        : definition(position, identifier), m_return_type(return_type), m_body(body), parameters(std::move(parameters))
     {
     }
 
@@ -448,6 +463,11 @@ namespace source
         return m_body;
     }
 
+    type_expression *procedure_definition::return_type()
+    {
+        return m_return_type;
+    }
+
     procedure_definition::~procedure_definition()
     {
         if (m_body != nullptr)
@@ -768,27 +788,27 @@ namespace source
         delete m_operand;
     }
 
-    call_statement::call_statement(const struct position position, const std::string& name)
-        : statement(position), m_name(name)
+    call_expression::call_expression(const struct position position, const std::string& name)
+        : expression(position), m_name(name)
     {
     }
 
-    void call_statement::accept(parser_visitor *visitor)
+    void call_expression::accept(parser_visitor *visitor)
     {
         visitor->visit(this);
     }
 
-    std::string& call_statement::name()
+    std::string& call_expression::name()
     {
         return m_name;
     }
 
-    std::vector<expression *>& call_statement::arguments()
+    std::vector<expression *>& call_expression::arguments()
     {
         return m_arguments;
     }
 
-    call_statement::~call_statement()
+    call_expression::~call_expression()
     {
         for (auto argument : m_arguments)
         {
@@ -796,8 +816,28 @@ namespace source
         }
     }
 
+    expression_statement::expression_statement(const struct position position, expression *body)
+        : statement(position), m_body(body)
+    {
+    }
+
+    void expression_statement::accept(parser_visitor *visitor)
+    {
+        visitor->visit(this);
+    }
+
+    expression& expression_statement::body()
+    {
+        return *m_body;
+    }
+
+    expression_statement::~expression_statement()
+    {
+        delete m_body;
+    }
+
     compound_statement::compound_statement(const struct position position, std::vector<statement *>&& statements)
-        : statement(position), statements(std::move(statements))
+        : node(position), statements(std::move(statements))
     {
     }
 
@@ -814,6 +854,29 @@ namespace source
         }
     }
 
+    return_statement::return_statement(const struct position position, expression *return_expression)
+        : statement(position), m_return_expression(return_expression)
+    {
+    }
+
+    void return_statement::accept(parser_visitor *visitor)
+    {
+        visitor->visit(this);
+    }
+
+    expression *return_statement::return_expression()
+    {
+        return m_return_expression;
+    }
+
+    return_statement::~return_statement()
+    {
+        if (m_return_expression != nullptr)
+        {
+            delete m_return_expression;
+        }
+    }
+
     void assign_statement::accept(parser_visitor *visitor)
     {
         visitor->visit(this);
diff --git a/source/lexer.ll b/source/lexer.ll
index 75c1925..9bbe55d 100644
--- a/source/lexer.ll
+++ b/source/lexer.ll
@@ -100,6 +100,9 @@ or                      {
 not                     {
                             return yy::parser::make_NOT(this->location);
                         }
+return                  {
+                            return yy::parser::make_RETURN(this->location);
+                        }
 [A-Za-z_][A-Za-z0-9_]*  {
                             return yy::parser::make_IDENTIFIER(yytext, this->location);
                         }
diff --git a/source/parser.yy b/source/parser.yy
index 06582bc..af6b388 100644
--- a/source/parser.yy
+++ b/source/parser.yy
@@ -62,7 +62,7 @@
 %token <std::string> CHARACTER "character"
 %token <std::string> STRING "string"
 %token <bool> BOOLEAN
-%token IF WHILE DO THEN ELSE
+%token IF WHILE DO THEN ELSE RETURN
 %token CONST VAR PROCEDURE ARRAY OF TYPE RECORD POINTER TO UNION
 %token BEGIN_BLOCK END_BLOCK EXTERN
 %token LEFT_PAREN RIGHT_PAREN LEFT_SQUARE RIGHT_SQUARE SEMICOLON DOT COMMA
@@ -82,9 +82,10 @@
 %type <std::vector<elna::source::expression *>> expressions actual_parameter_list;
 %type <elna::source::designator_expression *> designator_expression;
 %type <elna::source::assign_statement *> assign_statement;
-%type <elna::source::call_statement *> call_statement;
+%type <elna::source::call_expression *> call_expression;
 %type <elna::source::while_statement *> while_statement;
 %type <elna::source::if_statement *> if_statement;
+%type <elna::source::return_statement *> return_statement;
 %type <elna::source::statement *> statement;
 %type <std::vector<elna::source::statement *>> statements optional_statements;
 %type <elna::source::procedure_definition *> procedure_definition;
@@ -144,14 +145,22 @@ procedure_definition:
     PROCEDURE IDENTIFIER formal_parameter_list SEMICOLON block SEMICOLON
         {
             $$ = new elna::source::procedure_definition(elna::source::position{},
-                 std::move($2), $5);
-            std::swap($$->parameters, $3);
+                 $2, std::move($3), nullptr, $5);
         }
     | PROCEDURE IDENTIFIER formal_parameter_list SEMICOLON EXTERN SEMICOLON
         {
             $$ = new elna::source::procedure_definition(elna::source::position{},
-                 std::move($2));
-            std::swap($$->parameters, $3);
+                 $2, std::move($3), nullptr, nullptr);
+        }
+    | PROCEDURE IDENTIFIER formal_parameter_list COLON type_expression SEMICOLON block SEMICOLON
+        {
+            $$ = new elna::source::procedure_definition(elna::source::position{},
+                 $2, std::move($3), $5, $7);
+        }
+    | PROCEDURE IDENTIFIER formal_parameter_list COLON type_expression SEMICOLON EXTERN SEMICOLON
+        {
+            $$ = new elna::source::procedure_definition(elna::source::position{},
+                 $2, std::move($3), $5, nullptr);
         }
 procedure_definitions:
     procedure_definition procedure_definitions
@@ -167,9 +176,9 @@ assign_statement: designator_expression ASSIGNMENT expression
         {
             $$ = new elna::source::assign_statement(elna::source::make_position(@1), $1, $3);
         }
-call_statement: IDENTIFIER actual_parameter_list
+call_expression: IDENTIFIER actual_parameter_list
         {
-            $$ = new elna::source::call_statement(elna::source::make_position(@1), $1);
+            $$ = new elna::source::call_expression(elna::source::make_position(@1), $1);
             std::swap($$->arguments(), $2);
         }
 while_statement: WHILE expression DO optional_statements END_BLOCK
@@ -189,6 +198,11 @@ if_statement:
             auto _else = new elna::source::compound_statement(elna::source::make_position(@5), std::move($6));
             $$ = new elna::source::if_statement(elna::source::make_position(@1), $2, then, _else);
         }
+return_statement:
+    RETURN expression
+        {
+            $$ = new elna::source::return_statement(elna::source::make_position(@1), $2);
+        }
 literal:
     INTEGER
         {
@@ -282,6 +296,7 @@ expression:
             $$ = new elna::source::binary_expression(elna::source::make_position(@1), $1, $3, 'o');
         }
     | logical_operand { $$ = $1; }
+    | call_expression { $$ = $1; }
 expressions:
     expression COMMA expressions
         {
@@ -308,9 +323,10 @@ designator_expression:
         }
 statement:
     assign_statement { $$ = $1; }
-    | call_statement { $$ = $1; }
     | while_statement { $$ = $1; }
     | if_statement { $$ = $1; }
+    | return_statement { $$ = $1; }
+    | expression { $$ = new elna::source::expression_statement(elna::source::make_position(@1), $1); }
 statements:
     statement SEMICOLON statements
         {