>If I do a SET CLASSLIB TO whatever ADDITIVE in my startup program, will it be available to all my forms and procedures from there ?
>

Yes... or until you SET CLASSLIB without ADDITIVE.

>If I issue a second time a SET CLASSLIB ... of the same library, will it put it twice in memory ?
>

No... you can also check to see if your class is in SET CLASSLIB with something like...

If 'MYCLASS' $ Upper( Set( 'ClassLib) )

Also, you can use NewObject which will add the classlib to set classlib if it is not in the list.

>Thanks
>Eric.

HTH,
BOb