The electrochemical reduction of 1,2-di(4-pyridyl)ethylene has been examined between H 0 = -2 and pH 14. For pH > 6.5 a global 2e - , 3H + or 2e - , 2H + surface reversible reaction leads to the quinoidal form already proposed by Volke and Holubek (Coll. Czech. Chem. Commun. 27 (1962) 1777); it is followed by an internal transfer of two protons to give 1,2-di(4-pyridyl)ethane. The rate constant for this first order process varies from 47 s - 1 below pH 8.5 to 5.5 s - 1 above pH 11.5. The variations of the global rate constant of the electrochemical reaction with pH are analyzed; the process is controlled by the first 1e - stage; the elementary surface rate constants are larger than 2 10 5 s - 1 .