Electrode potentials are computed theoretically for quinones in aqueous solution by using density functional theory. The calculations are carried out at the DFT-B3LYP level with the inclusion of entropic and thermochemical corrections to yield free energies of redox reactions. The Polarizable Continuum Model is used to describe the solvent. The average error of calculation of electrode potentials is less than 0.05 V and is decreased compared to the average error of methods previously presented. Such first principles predictions of electrode potentials should be useful for predicting and interpreting electrode potentials for other systems. (C) 2004 Published by Elsevier B.V.