Ok thankyou,

The reason I raised this question was to do with _assign methods,
We identified a bug where if you pass an object to an _assign method, it does not release the handle on the object properly.
This caused problems with forms in particular, because they would not close under VFP7.

I identified a case-specific WorkAround, where if you did a
return m.vNewVal
at the end of the assign method it seemingly released the reference it was holding to the object.
This worked on a single class, but did not carry over when implemented into our class hierarchy.
Therefore I was wondering if maybe internally VFP was passing the object through each _assign method in the hirearchy and only releasing the object at the lowest base class level (the only one with code in it).
It is really something that the guys from MS would have to answer though I would guess as it is probably impossible for anyone simply using VFP to work this out.