Very thin films of natural rubber, polystyrene, and poly(methylmethacrylate) have been spun-cast on silicon wafers from dilute solutions of toluene and cyclohexane. Layers were uniform across the wafers, ranging from 0.5 to 170 nm, as measured by ellipsometry. Their average thickness e increased with solution concentration and decreased with rotational rate omega. Changing the volume of the solution pipetted onto the wafers did not affect the final thickness, whereas changing the solvent did. The previously reported empircal relation for much thicker films, e alpha omega - 1/2, held over the range investigated here.