i was reading about using Interfaces to achieve extensibility of COMs . but it looks like using VB 6 one can achieve extensibility without using custom interfaces . <BR><BR>i did the following --<BR>1. Make .dll using ObjectControl Interface ( NOT a custom interface ) in VB 6. Set project compatibility as Binary Compatible.Deploy it in MTS. <BR>2. Build a standard .Exe in VB6 and make use of method A of above COM .dll<BR>3. Check by a sample run . all is OK <BR><BR>4. Now add an extra argument in method A of COM . build .dll . Select Preserve Compatibility in vb when it warns about the change of method signature . <BR><BR>5. Refresh MTS package . Run the client .exe again . <BR>IT DOES WORK !!!<BR><BR>isn&#039;t it surprising ? does that mean if i use VB , i don&#039;t need to create custom interfaces to have my COMs extensible as my test shows i can run my old clients without any problem ? <BR><BR>For new clints , i can always make use of new method definition .<BR><BR>am i missing a point ? or just being bit lucky ? <BR>any help will be highly appreciated .<BR>milind <BR><BR>milind_dabhole@hotmail.com