The hydrogen evolution reaction (HER) has been studied at Raney nickel electrodes in the absence and presence of several organic compounds. A poisoning effect of nonreducible organic substrates on the kinetics of the HER was studied. It was found that only pyridine had a strong inhibiting effect on the HER. A compound having one reducible double bond, trans -cinnamic acid, was used as a model in a study of the mechanism of the electrocatalytics hydrogenation (ECH) reaction and its influence on the HER. It was established that the HER proceeds via the Volmer-Hyrovsky reaction mechanism, and the slowest step is the Heyrovsky reaction.