The surface-enhanced Raman spectra (SERS) of 2,3-dimethylpyrazine adsorbed on silver have been recorded at different electrode potentials. The main feature of the SERS spectra is the selective enhancement of the vibration 8a, while the remaining vibrations do not undergo any noticeable enhancement. This behavior has been explained according to a photoinduced charge transfer mechanism between the metal and the adsorbate, involving the ground electronic states of the neutral molecule (S 0 state) and the radical anion (D 0 state), given that the incoming photon induces the transfer of an electron from the Fermi level of the metal to vacant orbitals of the adsorbate.