Thank you for taking the time. I think I've managed to isolate the problem. (I say I think because I'm really new at this) Created an object (office unit) with multiple parts, using material with sub-object. I tried two processes. One, assigning the material to a particular surface with the edit mesh material ID. Two, assigning material with the Material modifier to the whole part although I only wanted one of the polys with the material (eg front face of a door, where I found the modifier only allows me to assign to the whole object). In the first case with the edit poly/mesh modifier, the poly count jumped. I have paid attention to your warnings about stacks, but I knew that I would be clearing them with the Collapse Utility. I hope that I've managed to clearly describe the process. Again, thanks for your trouble. Angela