Index: src/Boo.Lang.Compiler/Steps/MergePartialClasses.cs
===================================================================
--- src/Boo.Lang.Compiler/Steps/MergePartialClasses.cs	(revision 0)
+++ src/Boo.Lang.Compiler/Steps/MergePartialClasses.cs	(revision 0)
@@ -0,0 +1,119 @@
+#region license
+// Copyright (c) 2004, Rodrigo B. de Oliveira (rbo@acm.org)
+// All rights reserved.
+// 
+// Redistribution and use in source and binary forms, with or without modification,
+// are permitted provided that the following conditions are met:
+// 
+//     * Redistributions of source code must retain the above copyright notice,
+//     this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above copyright notice,
+//     this list of conditions and the following disclaimer in the documentation
+//     and/or other materials provided with the distribution.
+//     * Neither the name of Rodrigo B. de Oliveira nor the names of its
+//     contributors may be used to endorse or promote products derived from this
+//     software without specific prior written permission.
+// 
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
+// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+// THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+
+namespace Boo.Lang.Compiler.Steps
+{
+	using System;
+	using System.Collections;
+	using Boo.Lang.Compiler;
+	using Boo.Lang.Compiler.Ast;
+	using Boo.Lang.Compiler.TypeSystem;
+	using Attribute=Boo.Lang.Compiler.Ast.Attribute;
+
+	public class MergePartialClasses : AbstractNamespaceSensitiveTransformerCompilerStep
+	{
+		Hashtable _partials = new Hashtable();
+		ClassDefinition _current = null;
+		
+		override public void Run()
+		{			
+			Visit(CompileUnit.Modules);
+		}
+		
+		override public bool EnterClassDefinition(ClassDefinition node)
+		{
+			if (_partials.Contains(node.FullName))
+			{
+				_current = (ClassDefinition)_partials[node.FullName];
+				RemoveCurrentNode();
+				return true;
+			}
+			else
+			{
+				_partials[node.FullName] = node;
+				return false;
+			}
+		}
+		
+		override public void LeaveClassDefinition(ClassDefinition node)
+		{
+			_current = null;
+		}
+		
+		override public void OnAttribute(Attribute node)
+		{
+			if (_current != null)
+			{
+				//attributes for the merged class contain any and all attributes declared on each partial definition
+				_current.Attributes.Add(node);
+			}
+		}
+		
+		private void AddMember(TypeMember member)
+		{
+			if (_current != null)
+			{
+				_current.Members.Add(member);
+			}
+		}
+		
+		override public void OnStructDefinition(StructDefinition node) { AddMember(node); }
+		override public void OnInterfaceDefinition(InterfaceDefinition node) { AddMember(node); }
+		override public void OnEnumDefinition(EnumDefinition node) { AddMember(node); }
+		override public void OnField(Field node) { AddMember(node); }
+		override public void OnProperty(Property node) { AddMember(node); }
+		override public void OnEvent(Event node) { AddMember(node); }
+		override public void OnMethod(Method node) { AddMember(node); }
+		override public void OnConstructor(Constructor node) { AddMember(node); }
+		
+		
+		/* the simple type references that happen while visiting a 
+		 * class defintion are its base class and implemented interfaces
+		 * */
+		override public void OnSimpleTypeReference(SimpleTypeReference node) 
+		{
+			if (_current != null && !IsAlreadyAdded(_current.BaseTypes, node))
+			{
+				_current.BaseTypes.Add(node);
+			}
+		}
+		
+		private bool IsAlreadyAdded(TypeReferenceCollection col, SimpleTypeReference node)
+		{
+			foreach (SimpleTypeReference refer in col)
+			{
+				if (node.Name == refer.Name)
+				{
+					return true;
+				}
+			}
+			
+			return false;
+		}
+	}
+}
Index: src/Boo.Lang.Compiler/Pipelines/ResolveExpressions.cs
===================================================================
--- src/Boo.Lang.Compiler/Pipelines/ResolveExpressions.cs	(revision 1897)
+++ src/Boo.Lang.Compiler/Pipelines/ResolveExpressions.cs	(working copy)
@@ -36,6 +36,7 @@
 		{
 			Add(new InitializeTypeSystemServices());
 			Add(new PreErrorChecking());
+			Add(new MergePartialClasses());
 			Add(new InitializeNameResolutionService());
 			Add(new IntroduceGlobalNamespaces());
 			Add(new TransformCallableDefinitions());
@@ -59,5 +60,5 @@
 			Add(new ExpandAstLiterals());
 			Add(new ProcessMethodBodiesWithDuckTyping());
 		}
-	}
+	}
 }
Index: tests/testcases/integration/partial-1.boo
===================================================================
--- tests/testcases/integration/partial-1.boo	(revision 0)
+++ tests/testcases/integration/partial-1.boo	(revision 0)
@@ -0,0 +1,44 @@
+"""
+method1
+field1
+property1
+property2
+inheritedmethod
+method1
+"""
+
+interface ITest:
+	def method1()
+	
+class BaseClass:
+	def inheritedmethod():
+		print "inheritedmethod"
+
+class C:
+	def method1():
+		print "method1"
+	
+	Property1:
+		get:
+			return "property1"
+
+//this can be in a separate file
+class C(BaseClass, ITest):
+	public fld1 = "field1"
+	
+	def method2():
+		print "method2"
+		
+	Property2:
+		get:
+			return "property2"
+
+c = C()
+c.method1()
+print c.fld1
+print c.Property1
+print c.Property2
+c.inheritedmethod()
+test = c as ITest
+test.method1()
+