Sorry Animemi, I am posting exactly the same subject as you. I have the same problem (inverted normals) that probably comes from the use of booleans in 3DS Max. My object is quite complex, and I did it at least 3 times and still there is a problem. So I try with something (that I thought was) easier. But even with 2 cubes, I got the inverted normals and I cannot figure out where those inverted normals actually are. It drives me crazy. How can I fix a problem I cannot see? I try with edit normals in 3DS MAx and all seems fine. And I can see no hidden geometry, no overlapping faces. So, what wrong ? Can anyone help me, please? Thanks.