By using the previously developed roughening method for producing SERS-active Rh electrode, and assisted by the highly sensitive confocal microprobe Raman system, we carried out a detailed SERS study on the dissociation and electrooxidation of C-1 molecules on a Rh surface. The SERS spectra obtained in a wide frequency region provide not only the vibrations reflecting the internal bonding of CO (at ca. 2000 cm(-1)) but also the bonding between CO or O with Rh (at ca. 450 cm(-1)). A complementary electrochemical study was also performed on the roughened Rh surface in order to correlate the electrochemical and vibrational information. Both electrochemical and SERS studies show that Rh has no discernible activity toward the electrooxidation or dissociation of methanol in acidic solutions. Rh becomes active and its activity increases with the decrease of the solution acidity. For HCHO and HCOOH, the electrooxidation activity of Rh increases with increasing pH. On the basis of the result of the model CO system, discussion on the dissociation or electrooxidation mechanisms was presented for C-1 molecules on Rh.