>Claude,
>I try to create Serviced .NET component in VB.NET.
>In that component I want to create additional thread for calculation purposes.
>But I can not find any clue on how to create MTDLL (multithreaded dll) in VB.NET

Any COM DLL you create with .Net is automatically an MTDLL...

There's more info on how to create .NET Com DLLs here:

http://www.west-wind.com/presentations/VfpDotNetInterop/DotNetFromVFP.asp

+++ Rick ---