Large deviations from the behavior predicted by the Butler−Volmer equation of electrochemistry are accountedfor using mesoscopic nonequilibrium thermodynamics. The nonequilibrium thermodynamic hypotheses areextended to include velocity space and cope with imperfect reactant transport leading to departures fromButler−Volmer behavior. This results in a modified Butler−Volmer equation in good agreement withexperimental data. The distinct advantages of the method and its applicability to analyze other systems arebriefly discussed.