We have examined how much the photolysis of 4-nitrobenzenethiol (4-NBT) to 4-aminobenzenethiol on Ag by visible light is affected by the nano-and atomic-scale roughness features of silver which are deeply associated with the electromagnetic (EM) and chemical (CHEM) enhancement mechanisms, respectively, in surface-enhanced Raman scattering. Both the CHEM and EM sites were indeed involved in the surface-induced photoreaction of 4-NBT on Ag, and the contribution of EM-sites to the overall photolysis appeared to be as much as similar to65%. These findings are in conformity with the fact that the photoelectron emission is strongly affected by the extent of the roughening specifically for Ag, which has a quite low oxidation potential. (C) 2003 Elsevier B.V. All rights reserved.