The electrochemical reduction of dimethyl maleate (DMF) and dimethyl fumarate (Dh IF) in acetonitrile and methanol solutions has been investigated using cyclic voltammetry (CV), rotating ring-disk electrode voltammetry (RRDE) and in situ FT-IR spectroelectrochemistry. In both solvents, the electrochemically generated radical anion of DMM under goes both a rapid cis-trans isomerisation process forming the dimethyl fumarate radical anion (DMF.-) and a rapid radical anion dimerisation reaction. The radical anion dimerisation of these species is rapid with second order rate constants of approximate to 1 x 10(7) mol dm(-3) s(-1). An autocatalytic electron cross-exchange reaction between the DMF.- species and DMM results in DMF and DMM- consequently leading to a rapid build-up of the trans isomer in solution.