Rates of electron-transfer between redox reactants located on opposite sides of the interface between thin layers of organic solvents on graphite electrode and aqueous solutions were measured by means of steady-state electrochemistry. Changes in the overall driving forces for irreversible reactions produced changes in rate that fit no simple behavioral pattern. For reversible reactions, a regular increase in rate with driving force was obtained. Evidence for a significant effect of diffuse-layer potentials on reaction rates was not found.