Yes, but why VS2008 did not make this a problem on compiling? I agree with you when you say you can't use upper framework form a 2.0 assembly, 'cause, for example it can be deployed on a win2000 or on a machine without .NET 3.0. But as I say in my previous post, I'll deploy this solution on .NET 3.5 ready machines; only a bug/limit of Cobol<->.NET bridge force me to compile only this Cobol-.NET-interface-assembly in 2.0. However, I found the trick: reference System.Core.dll (or other dll needed by your referenced assemblies) by hand. Thanks! Nando Jesus