We have studied on the SERS spectra of pyridine in various electrochemical systems: 0.05 M pyridine/0.1 M KCl/water/Ag, 0.05 M pyridine/0.1 M LiCl/alcohols/Ag, 0.05 M pyridine/0.002 M KCl/methanol/Ag. Surface carbons were found to be just one of the surface adsorbates and not the prerequisite for SERS observation. Time dependence of SERS intensity build-up during the reduction period of the anodized electrode surface and the SERS intensity dependence on the electrolyte concentration suggest the importance of the adatomic cluster formation.