diff --git a/ICSharpCode.NRefactory.Tests/ICSharpCode.NRefactory.Tests.csproj b/ICSharpCode.NRefactory.Tests/ICSharpCode.NRefactory.Tests.csproj
index 407f7dc19b..9b68806161 100644
--- a/ICSharpCode.NRefactory.Tests/ICSharpCode.NRefactory.Tests.csproj
+++ b/ICSharpCode.NRefactory.Tests/ICSharpCode.NRefactory.Tests.csproj
@@ -191,6 +191,7 @@
     <Compile Include="TypeSystem\CecilLoaderTests.cs" />
     <Compile Include="TypeSystem\GetAllBaseTypesTest.cs" />
     <Compile Include="TypeSystem\GetMembersTests.cs" />
+    <Compile Include="TypeSystem\LazyLoadedCecilLoaderTests.cs" />
     <Compile Include="TypeSystem\ReflectionHelperTests.cs" />
     <Compile Include="TypeSystem\SerializedCecilLoaderTests.cs" />
     <Compile Include="TypeSystem\StructureTests.cs" />
diff --git a/ICSharpCode.NRefactory.Tests/TypeSystem/LazyLoadedCecilLoaderTests.cs b/ICSharpCode.NRefactory.Tests/TypeSystem/LazyLoadedCecilLoaderTests.cs
new file mode 100644
index 0000000000..2000207509
--- /dev/null
+++ b/ICSharpCode.NRefactory.Tests/TypeSystem/LazyLoadedCecilLoaderTests.cs
@@ -0,0 +1,36 @@
+// Copyright (c) AlphaSierraPapa for the SharpDevelop Team
+// 
+// Permission is hereby granted, free of charge, to any person obtaining a copy of this
+// software and associated documentation files (the "Software"), to deal in the Software
+// without restriction, including without limitation the rights to use, copy, modify, merge,
+// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
+// to whom the Software is furnished to do so, subject to the following conditions:
+// 
+// The above copyright notice and this permission notice shall be included in all copies or
+// substantial portions of the Software.
+// 
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
+// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
+// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+using System;
+using ICSharpCode.NRefactory.TypeSystem.Implementation;
+using NUnit.Framework;
+
+namespace ICSharpCode.NRefactory.TypeSystem
+{
+	[TestFixture]
+	public class LazyLoadedCecilLoaderTests : TypeSystemTests
+	{
+		[TestFixtureSetUp]
+		public void FixtureSetUp()
+		{
+			CecilLoader loader = new CecilLoader() { IncludeInternalMembers = true, LazyLoad = true };
+			IUnresolvedAssembly pc = loader.LoadAssemblyFile(typeof(TestCase.SimplePublicClass).Assembly.Location);
+			base.compilation = new SimpleCompilation(pc, CecilLoaderTests.Mscorlib);
+		}
+	}
+}
diff --git a/ICSharpCode.NRefactory/TypeSystem/CecilLoader.cs b/ICSharpCode.NRefactory/TypeSystem/CecilLoader.cs
index aa60bd995c..8b97a43897 100644
--- a/ICSharpCode.NRefactory/TypeSystem/CecilLoader.cs
+++ b/ICSharpCode.NRefactory/TypeSystem/CecilLoader.cs
@@ -47,6 +47,16 @@ namespace ICSharpCode.NRefactory.TypeSystem
 		/// </summary>
 		public bool IncludeInternalMembers { get; set; }
 		
+		/// <summary>
+		/// Specifies whether to use lazy loading. The default is false.
+		/// If this property is set to true, the CecilLoader will not copy all the relevant information
+		/// out of the Cecil object model, but will maintain references to the Cecil objects.
+		/// This speeds up the loading process and avoids loading unnecessary information, but it causes
+		/// the Cecil objects to stay in memory (which can significantly increase memory usage).
+		/// It also prevents serialization of the Cecil-loaded type system.
+		/// </summary>
+		public bool LazyLoad { get; set; }
+		
 		/// <summary>
 		/// Gets/Sets the documentation provider that is used to retrieve the XML documentation for all members.
 		/// </summary>
@@ -137,7 +147,7 @@ namespace ICSharpCode.NRefactory.TypeSystem
 					this.CancellationToken.ThrowIfCancellationRequested();
 					if (this.IncludeInternalMembers || (td.Attributes & TypeAttributes.VisibilityMask) == TypeAttributes.Public) {
 						string name = td.Name;
-						if (name.Length == 0 || name[0] == '<')
+						if (name.Length == 0)
 							continue;
 						
 						var t = CreateTopLevelTypeDefinition(td);
@@ -166,6 +176,7 @@ namespace ICSharpCode.NRefactory.TypeSystem
 		/// This causes ReadTypeReference() to use <see cref="DefaultAssemblyReference.CurrentAssembly"/> for references
 		/// in that module.
 		/// </summary>
+		[CLSCompliant(false)]
 		public void SetCurrentModule(ModuleDefinition module)
 		{
 			this.currentModule = module;
@@ -1449,65 +1460,76 @@ namespace ICSharpCode.NRefactory.TypeSystem
 		{
 			string name = ReflectionHelper.SplitTypeParameterCountFromReflectionName(typeDefinition.Name);
 			var td = new DefaultUnresolvedTypeDefinition(typeDefinition.Namespace, name);
-			InitTypeParameters(typeDefinition, td);
+			if (typeDefinition.HasGenericParameters)
+				InitTypeParameters(typeDefinition, td.TypeParameters);
 			return td;
 		}
 		
-		static void InitTypeParameters(TypeDefinition typeDefinition, DefaultUnresolvedTypeDefinition td)
+		static void InitTypeParameters(TypeDefinition typeDefinition, IList<IUnresolvedTypeParameter> typeParameters)
 		{
 			// Type parameters are initialized within the constructor so that the class can be put into the type storage
 			// before the rest of the initialization runs - this allows it to be available for early binding as soon as possible.
 			for (int i = 0; i < typeDefinition.GenericParameters.Count; i++) {
 				if (typeDefinition.GenericParameters[i].Position != i)
 					throw new InvalidOperationException("g.Position != i");
-				td.TypeParameters.Add(new DefaultUnresolvedTypeParameter(
+				typeParameters.Add(new DefaultUnresolvedTypeParameter(
 					EntityType.TypeDefinition, i, typeDefinition.GenericParameters[i].Name));
 			}
 		}
 		
+		void InitTypeParameterConstraints(TypeDefinition typeDefinition, IList<IUnresolvedTypeParameter> typeParameters)
+		{
+			for (int i = 0; i < typeParameters.Count; i++) {
+				AddConstraints((DefaultUnresolvedTypeParameter)typeParameters[i], typeDefinition.GenericParameters[i]);
+			}
+		}
+		
 		void InitTypeDefinition(TypeDefinition typeDefinition, DefaultUnresolvedTypeDefinition td)
 		{
+			td.Kind = GetTypeKind(typeDefinition);
 			InitTypeModifiers(typeDefinition, td);
+			InitTypeParameterConstraints(typeDefinition, td.TypeParameters);
 			
-			if (typeDefinition.HasGenericParameters) {
-				for (int i = 0; i < typeDefinition.GenericParameters.Count; i++) {
-					AddConstraints((DefaultUnresolvedTypeParameter)td.TypeParameters[i], typeDefinition.GenericParameters[i]);
-				}
-			}
-			
-			InitNestedTypes(typeDefinition, td); // nested types can be initialized only after generic parameters were created
+			// nested types can be initialized only after generic parameters were created
+			InitNestedTypes(typeDefinition, td, td.NestedTypes);
 			AddAttributes(typeDefinition, td);
 			td.HasExtensionMethods = HasExtensionAttribute(typeDefinition);
 			
+			InitBaseTypes(typeDefinition, td.BaseTypes);
+			
+			td.AddDefaultConstructorIfRequired = (td.Kind == TypeKind.Struct || td.Kind == TypeKind.Enum);
+			InitMembers(typeDefinition, td, td.Members);
+			if (HasCecilReferences)
+				typeSystemTranslationTable[td] = typeDefinition;
+			if (this.InterningProvider != null) {
+				td.ApplyInterningProvider(this.InterningProvider);
+			}
+			td.Freeze();
+		}
+		
+		void InitBaseTypes(TypeDefinition typeDefinition, IList<ITypeReference> baseTypes)
+		{
 			// set base classes
 			if (typeDefinition.IsEnum) {
 				foreach (FieldDefinition enumField in typeDefinition.Fields) {
 					if (!enumField.IsStatic) {
-						td.BaseTypes.Add(ReadTypeReference(enumField.FieldType));
+						baseTypes.Add(ReadTypeReference(enumField.FieldType));
 						break;
 					}
 				}
 			} else {
 				if (typeDefinition.BaseType != null) {
-					td.BaseTypes.Add(ReadTypeReference(typeDefinition.BaseType));
+					baseTypes.Add(ReadTypeReference(typeDefinition.BaseType));
 				}
 				if (typeDefinition.HasInterfaces) {
 					foreach (TypeReference iface in typeDefinition.Interfaces) {
-						td.BaseTypes.Add(ReadTypeReference(iface));
+						baseTypes.Add(ReadTypeReference(iface));
 					}
 				}
 			}
-			
-			InitMembers(typeDefinition, td);
-			if (HasCecilReferences)
-				typeSystemTranslationTable[td] = typeDefinition;
-			if (this.InterningProvider != null) {
-				td.ApplyInterningProvider(this.InterningProvider);
-			}
-			td.Freeze();
 		}
 		
-		void InitNestedTypes(TypeDefinition typeDefinition, DefaultUnresolvedTypeDefinition td)
+		void InitNestedTypes(TypeDefinition typeDefinition, IUnresolvedTypeDefinition declaringTypeDefinition, IList<IUnresolvedTypeDefinition> nestedTypes)
 		{
 			if (!typeDefinition.HasNestedTypes)
 				return;
@@ -1522,33 +1544,35 @@ namespace ICSharpCode.NRefactory.TypeSystem
 					int pos = name.LastIndexOf('/');
 					if (pos > 0)
 						name = name.Substring(pos + 1);
-					if (name.Length == 0 || name[0] == '<')
-						continue;
 					name = ReflectionHelper.SplitTypeParameterCountFromReflectionName(name);
-					var nestedType = new DefaultUnresolvedTypeDefinition(td, name);
-					InitTypeParameters(nestedTypeDef, nestedType);
-					td.NestedTypes.Add(nestedType);
+					var nestedType = new DefaultUnresolvedTypeDefinition(declaringTypeDefinition, name);
+					InitTypeParameters(nestedTypeDef, nestedType.TypeParameters);
+					nestedTypes.Add(nestedType);
 					InitTypeDefinition(nestedTypeDef, nestedType);
 				}
 			}
 		}
 		
-		static void InitTypeModifiers(TypeDefinition typeDefinition, DefaultUnresolvedTypeDefinition td)
+		static TypeKind GetTypeKind(TypeDefinition typeDefinition)
 		{
 			// set classtype
 			if (typeDefinition.IsInterface) {
-				td.Kind = TypeKind.Interface;
+				return TypeKind.Interface;
 			} else if (typeDefinition.IsEnum) {
-				td.Kind = TypeKind.Enum;
+				return TypeKind.Enum;
 			} else if (typeDefinition.IsValueType) {
-				td.Kind = TypeKind.Struct;
+				return TypeKind.Struct;
 			} else if (IsDelegate(typeDefinition)) {
-				td.Kind = TypeKind.Delegate;
+				return TypeKind.Delegate;
 			} else if (IsModule(typeDefinition)) {
-				td.Kind = TypeKind.Module;
+				return TypeKind.Module;
 			} else {
-				td.Kind = TypeKind.Class;
+				return TypeKind.Class;
 			}
+		}
+		
+		static void InitTypeModifiers(TypeDefinition typeDefinition, AbstractUnresolvedEntity td)
+		{
 			td.IsSealed = typeDefinition.IsSealed;
 			td.IsAbstract = typeDefinition.IsAbstract;
 			switch (typeDefinition.Attributes & TypeAttributes.VisibilityMask) {
@@ -1598,9 +1622,8 @@ namespace ICSharpCode.NRefactory.TypeSystem
 			return false;
 		}
 		
-		void InitMembers(TypeDefinition typeDefinition, DefaultUnresolvedTypeDefinition td)
+		void InitMembers(TypeDefinition typeDefinition, IUnresolvedTypeDefinition td, IList<IUnresolvedMember> members)
 		{
-			td.AddDefaultConstructorIfRequired = (td.Kind == TypeKind.Struct || td.Kind == TypeKind.Enum);
 			if (typeDefinition.HasMethods) {
 				foreach (MethodDefinition method in typeDefinition.Methods) {
 					if (IsVisible(method.Attributes) && !IsAccessor(method.SemanticsAttributes)) {
@@ -1611,14 +1634,14 @@ namespace ICSharpCode.NRefactory.TypeSystem
 							else if (method.Name.StartsWith("op_", StringComparison.Ordinal))
 								type = EntityType.Operator;
 						}
-						td.Members.Add(ReadMethod(method, td, type));
+						members.Add(ReadMethod(method, td, type));
 					}
 				}
 			}
 			if (typeDefinition.HasFields) {
 				foreach (FieldDefinition field in typeDefinition.Fields) {
 					if (IsVisible(field.Attributes) && !field.IsSpecialName) {
-						td.Members.Add(ReadField(field, td));
+						members.Add(ReadField(field, td));
 					}
 				}
 			}
@@ -1634,14 +1657,14 @@ namespace ICSharpCode.NRefactory.TypeSystem
 					bool setterVisible = property.SetMethod != null && IsVisible(property.SetMethod.Attributes);
 					if (getterVisible || setterVisible) {
 						EntityType type = property.Name == defaultMemberName ? EntityType.Indexer : EntityType.Property;
-						td.Members.Add(ReadProperty(property, td, type));
+						members.Add(ReadProperty(property, td, type));
 					}
 				}
 			}
 			if (typeDefinition.HasEvents) {
 				foreach (EventDefinition ev in typeDefinition.Events) {
 					if (ev.AddMethod != null && IsVisible(ev.AddMethod.Attributes)) {
-						td.Members.Add(ReadEvent(ev, td));
+						members.Add(ReadEvent(ev, td));
 					}
 				}
 			}
@@ -1653,6 +1676,140 @@ namespace ICSharpCode.NRefactory.TypeSystem
 		}
 		#endregion
 		
+		#region Lazy-Loaded Type Definition
+		sealed class LazyCecilTypeDefinition : AbstractUnresolvedEntity, IUnresolvedTypeDefinition
+		{
+			readonly CecilLoader loader;
+			readonly string namespaceName;
+			readonly TypeDefinition cecilTypeDef;
+			readonly TypeKind kind;
+			readonly IList<IUnresolvedTypeParameter> typeParameters;
+			
+			IList<ITypeReference> baseTypes;
+			IList<IUnresolvedTypeDefinition> nestedTypes;
+			IList<IUnresolvedMember> members;
+			
+			public LazyCecilTypeDefinition(CecilLoader loader, TypeDefinition typeDefinition)
+			{
+				this.loader = loader;
+				this.cecilTypeDef = typeDefinition;
+				this.EntityType = EntityType.TypeDefinition;
+				this.namespaceName = cecilTypeDef.Namespace;
+				this.Name = ReflectionHelper.SplitTypeParameterCountFromReflectionName(cecilTypeDef.Name);
+				var tps = new List<IUnresolvedTypeParameter>();
+				InitTypeParameters(cecilTypeDef, tps);
+				this.typeParameters = FreezableHelper.FreezeList(tps);
+				
+				this.kind = GetTypeKind(typeDefinition);
+				InitTypeModifiers(typeDefinition, this);
+				loader.InitTypeParameterConstraints(typeDefinition, typeParameters);
+				
+				loader.AddAttributes(typeDefinition, this);
+				flags[FlagHasExtensionMethods] = HasExtensionAttribute(typeDefinition);
+				
+				if (loader.HasCecilReferences)
+					loader.typeSystemTranslationTable[this] = typeDefinition;
+				if (loader.InterningProvider != null) {
+					this.ApplyInterningProvider(loader.InterningProvider);
+				}
+				this.Freeze();
+			}
+			
+			public override string Namespace {
+				get { return namespaceName; }
+				set { throw new NotSupportedException(); }
+			}
+			
+			public TypeKind Kind {
+				get { return kind; }
+			}
+			
+			public IList<IUnresolvedTypeParameter> TypeParameters {
+				get { return typeParameters; }
+			}
+			
+			public IList<ITypeReference> BaseTypes {
+				get {
+					var result = LazyInit.VolatileRead(ref this.baseTypes);
+					if (result != null) {
+						return result;
+					} else {
+						result = new List<ITypeReference>();
+						loader.InitBaseTypes(cecilTypeDef, result);
+						return LazyInit.GetOrSet(ref this.baseTypes, FreezableHelper.FreezeList(result));
+					}
+				}
+			}
+			
+			public IList<IUnresolvedTypeDefinition> NestedTypes {
+				get {
+					var result = LazyInit.VolatileRead(ref this.nestedTypes);
+					if (result != null) {
+						return result;
+					} else {
+						result = new List<IUnresolvedTypeDefinition>();
+						loader.InitNestedTypes(cecilTypeDef, this, result);
+						return LazyInit.GetOrSet(ref this.nestedTypes, FreezableHelper.FreezeList(result));
+					}
+				}
+			}
+			
+			public IList<IUnresolvedMember> Members {
+				get {
+					var result = LazyInit.VolatileRead(ref this.members);
+					if (result != null) {
+						return result;
+					} else {
+						result = new List<IUnresolvedMember>();
+						loader.InitMembers(cecilTypeDef, this, result);
+						return LazyInit.GetOrSet(ref this.members, FreezableHelper.FreezeList(result));
+					}
+				}
+			}
+			
+			public IEnumerable<IUnresolvedMethod> Methods {
+				get { return Members.OfType<IUnresolvedMethod>(); }
+			}
+			
+			public IEnumerable<IUnresolvedProperty> Properties {
+				get { return Members.OfType<IUnresolvedProperty>(); }
+			}
+			
+			public IEnumerable<IUnresolvedField> Fields {
+				get { return Members.OfType<IUnresolvedField>(); }
+			}
+			
+			public IEnumerable<IUnresolvedEvent> Events {
+				get { return Members.OfType<IUnresolvedEvent>(); }
+			}
+			
+			public bool AddDefaultConstructorIfRequired {
+				get { return kind == TypeKind.Struct || kind == TypeKind.Enum; }
+			}
+			
+			public bool? HasExtensionMethods {
+				get { return flags[FlagHasExtensionMethods]; }
+				// we always return true or false, never null.
+				// FlagHasNoExtensionMethods is unused in LazyCecilTypeDefinition
+			}
+			
+			public IType Resolve(ITypeResolveContext context)
+			{
+				if (context == null)
+					throw new ArgumentNullException("context");
+				if (context.CurrentAssembly == null)
+					throw new ArgumentException("An ITypeDefinition cannot be resolved in a context without a current assembly.");
+				return context.CurrentAssembly.GetTypeDefinition(this)
+					?? (IType)new UnknownType(this.Namespace, this.Name, this.TypeParameters.Count);
+			}
+			
+			public ITypeResolveContext CreateResolveContext(ITypeResolveContext parentContext)
+			{
+				return parentContext;
+			}
+		}
+		#endregion
+		
 		#region Read Method
 		[CLSCompliant(false)]
 		public IUnresolvedMethod ReadMethod(MethodDefinition method, IUnresolvedTypeDefinition parentType, EntityType methodType = EntityType.Method)
diff --git a/ICSharpCode.NRefactory/TypeSystem/ITypeDefinition.cs b/ICSharpCode.NRefactory/TypeSystem/ITypeDefinition.cs
index 508f9ce810..1438505d8b 100644
--- a/ICSharpCode.NRefactory/TypeSystem/ITypeDefinition.cs
+++ b/ICSharpCode.NRefactory/TypeSystem/ITypeDefinition.cs
@@ -48,6 +48,12 @@ namespace ICSharpCode.NRefactory.TypeSystem
 		/// </summary>
 		bool? HasExtensionMethods { get; }
 		
+		/// <summary>
+		/// Gets whether this unresolved type definition causes the addition of a default constructor
+		/// if no other constructor is present.
+		/// </summary>
+		bool AddDefaultConstructorIfRequired { get; }
+		
 		/// <summary>
 		/// Looks up the resolved type definition from the <paramref name="context"/> corresponding to this unresolved
 		/// type definition.
diff --git a/ICSharpCode.NRefactory/TypeSystem/Implementation/AbstractUnresolvedEntity.cs b/ICSharpCode.NRefactory/TypeSystem/Implementation/AbstractUnresolvedEntity.cs
index d0a040e454..66d29b8c0c 100644
--- a/ICSharpCode.NRefactory/TypeSystem/Implementation/AbstractUnresolvedEntity.cs
+++ b/ICSharpCode.NRefactory/TypeSystem/Implementation/AbstractUnresolvedEntity.cs
@@ -50,7 +50,7 @@ namespace ICSharpCode.NRefactory.TypeSystem.Implementation
 		internal const ushort FlagShadowing = 0x0008;
 		internal const ushort FlagSynthetic = 0x0010;
 		internal const ushort FlagStatic    = 0x0020;
-		// flags for DefaultUnresolvedTypeDefinition
+		// flags for DefaultUnresolvedTypeDefinition/LazyCecilTypeDefinition
 		internal const ushort FlagAddDefaultConstructorIfRequired = 0x0040;
 		internal const ushort FlagHasExtensionMethods = 0x0080;
 		internal const ushort FlagHasNoExtensionMethods = 0x0100;
diff --git a/ICSharpCode.NRefactory/TypeSystem/Implementation/DefaultResolvedTypeDefinition.cs b/ICSharpCode.NRefactory/TypeSystem/Implementation/DefaultResolvedTypeDefinition.cs
index c4fb589e9b..4ea28dbe69 100644
--- a/ICSharpCode.NRefactory/TypeSystem/Implementation/DefaultResolvedTypeDefinition.cs
+++ b/ICSharpCode.NRefactory/TypeSystem/Implementation/DefaultResolvedTypeDefinition.cs
@@ -322,10 +322,7 @@ namespace ICSharpCode.NRefactory.TypeSystem.Implementation
 					}
 				}
 				
-				DefaultUnresolvedTypeDefinition dutd = part as DefaultUnresolvedTypeDefinition;
-				if (dutd != null) {
-					addDefaultConstructorIfRequired |= dutd.AddDefaultConstructorIfRequired;
-				}
+				addDefaultConstructorIfRequired |= part.AddDefaultConstructorIfRequired;
 			}
 			if (addDefaultConstructorIfRequired) {
 				TypeKind kind = this.Kind;