I'm not sure this is due to the number of materials used. Before answering you I have loaded a heavy plant from Tucan with only one material applied to the entire plant (a bitmap). I have then multiplicated the plant 7 times, have created a sphere and applied the same bitmap. Then I have double-clicked for the sphere in the material window to open the material editor, have changed the material to procedural, with some "special effects". This already slowed down the editor extremely. That's why I think this is a polygon problem, but I'm not sure either. Guitta