diff --git a/ownlang-parser/src/main/java/com/annimon/ownlang/parser/optimization/OptimizationVisitor.java b/ownlang-parser/src/main/java/com/annimon/ownlang/parser/optimization/OptimizationVisitor.java
index fee1831..0f15305 100644
--- a/ownlang-parser/src/main/java/com/annimon/ownlang/parser/optimization/OptimizationVisitor.java
+++ b/ownlang-parser/src/main/java/com/annimon/ownlang/parser/optimization/OptimizationVisitor.java
@@ -75,7 +75,33 @@ public abstract class OptimizationVisitor<T> implements ResultVisitor<Node, T> {
 
     @Override
     public Node visit(ClassDeclarationStatement s, T t) {
-        // TODO fields and methods
+        final var newClassDeclaration = new ClassDeclarationStatement(s.name);
+        boolean changed = false;
+        for (AssignmentExpression field : s.fields) {
+            final Node fieldExpr = field.expression.accept(this, t);
+            final AssignmentExpression newField;
+            if (fieldExpr != field.expression) {
+                changed = true;
+                newField = new AssignmentExpression(field.operation, field.target, fieldExpr);
+            } else {
+                newField = field;
+            }
+            newClassDeclaration.addField(newField);
+        }
+
+        for (FunctionDefineStatement method : s.methods) {
+            final var newMethod = method.accept(this, t);
+            if (newMethod != method) {
+                changed = true;
+                newClassDeclaration.addMethod((FunctionDefineStatement) newMethod);
+            } else {
+                newClassDeclaration.addMethod(method);
+            }
+        }
+
+        if (changed) {
+            return newClassDeclaration;
+        }
         return s;
     }
     
diff --git a/ownlang-parser/src/main/java/com/annimon/ownlang/parser/visitors/AbstractVisitor.java b/ownlang-parser/src/main/java/com/annimon/ownlang/parser/visitors/AbstractVisitor.java
index c352b37..5bc53ea 100644
--- a/ownlang-parser/src/main/java/com/annimon/ownlang/parser/visitors/AbstractVisitor.java
+++ b/ownlang-parser/src/main/java/com/annimon/ownlang/parser/visitors/AbstractVisitor.java
@@ -41,7 +41,12 @@ public abstract class AbstractVisitor implements Visitor {
 
     @Override
     public void visit(ClassDeclarationStatement s) {
-        
+        for (Node field : s.fields) {
+            field.accept(this);
+        }
+        for (Node method : s.methods) {
+            method.accept(this);
+        }
     }
 
     @Override
diff --git a/ownlang-parser/src/main/java/com/annimon/ownlang/parser/visitors/FunctionAdder.java b/ownlang-parser/src/main/java/com/annimon/ownlang/parser/visitors/FunctionAdder.java
index 2f90515..7f03cb2 100644
--- a/ownlang-parser/src/main/java/com/annimon/ownlang/parser/visitors/FunctionAdder.java
+++ b/ownlang-parser/src/main/java/com/annimon/ownlang/parser/visitors/FunctionAdder.java
@@ -13,4 +13,9 @@ public final class FunctionAdder extends AbstractVisitor {
         super.visit(s);
         s.eval();
     }
+
+    @Override
+    public void visit(ClassDeclarationStatement s) {
+        // skip, otherwise class methods will be visible outside of class
+    }
 }
diff --git a/ownlang-parser/src/test/java/com/annimon/ownlang/parser/ProgramsTest.java b/ownlang-parser/src/test/java/com/annimon/ownlang/parser/ProgramsTest.java
index af113af..d08787d 100644
--- a/ownlang-parser/src/test/java/com/annimon/ownlang/parser/ProgramsTest.java
+++ b/ownlang-parser/src/test/java/com/annimon/ownlang/parser/ProgramsTest.java
@@ -5,6 +5,7 @@ import com.annimon.ownlang.exceptions.OwnLangParserException;
 import com.annimon.ownlang.lib.FunctionValue;
 import com.annimon.ownlang.lib.NumberValue;
 import com.annimon.ownlang.lib.ScopeHandler;
+import com.annimon.ownlang.parser.ast.ClassDeclarationStatement;
 import com.annimon.ownlang.parser.ast.FunctionDefineStatement;
 import com.annimon.ownlang.parser.ast.Node;
 import com.annimon.ownlang.parser.ast.Visitor;
@@ -115,5 +116,10 @@ public class ProgramsTest {
                 }
             }
         }
+
+        @Override
+        public void visit(ClassDeclarationStatement s) {
+
+        }
     };
 }