Surface-enhanced Raman spectroscopy (SERS) studies have been successfully extended to Pt electrodes in a nonaqueous solution. The acetonitrile decomposition in 0.1 M LiClO4+CH3CN and the adsorption behavior of the resulting cyanide ions at a Pt electrode surface have been studied as a function of applied potential by using the SERS technique. Results show that acetonitrile decomposition occurs at a certain more negative potential by the appearance of the 2115 and 2147 cm(-1) bands assigned to CN stretching modes. Evidence is presented to suggest that a photoelectrochemical reduction of acetonitrile may occur. By adding water or pyridine to CH3CN, the decomposition reduction occurs at more negative potentials, suggesting a competitive adsorption at the Pt electrode surface. Two different adsorption configurations of the resulting cyanide ions: the types CN-...Li+ and CN-...CH3CN, are proposed to explain the spectral features and changes with potential.