The electrochemical reduction of pyrazine (pz) on a silver electrode from a 1.0 M KBr solution has been investigated by surface enhanced Raman scattering (SERS). New bands from products of reduced pyrazine were observed at potentials more negative than -900 mV (vs. SCE). The main product is believed to be the 1,4-dihydropyrazine cation (DHPz ⁺ ). The reduction is not completly reversible. It is clear from the observed spectroscopic and electrochemical data that some of the DHPz ⁺ was not re-oxidized when the potential scan was switched to positive values. This DHPz ⁺ (or one of its derivatives with similar structure) remained trapped on the electrode surface even at potentials more positive than the point of zero charge (pzc) of silver in this medium. It is proposed that the cation binds to adsorbed halide at potentials more positive than the pzc. The presence of reduced pyrazine products at potentials more positive than the pzc can lead to misinterpretations of the SER spectrum of pyrazine.