Thermodynamic and kinetic aspects of the electrochemistry of L-cystine reduction and L-cysteine oxidation are reviewed. Both mercury and a range of solid electrodes are considered. In the former case, cysteinate complex formation occurs; in the case of solid electrodes, reactant adsorption is a complicating factor. At both types of electrode, the kinetics of electron transfer and mass transport of reactant can become an important rate-determining step. The implications of thermodynamic and kinetic studies on the electrosynthesis of L-cysteine are highlighted.