Hi Brian,

>>>I can not duplicate that boolean problem?
Can you explain specifically how you had it happen? I tried all sorts of angles without problems.

I have just re-checked on a restored image of a clean installation of XP, but still seeing the same problem

When you looked at this, did you attempt to union 2 pipes created from sweep (or the pipe command from Michael).
I know that a union of 2 solid cylinders does work correctly.(but I am looking at this from the point of sweep/pipe along projected lines)

- Steve