The half-wave reduction potentials of a series of substituted benzyl bromides show a linear correlation with Hammett σ substituent values with ρ=+0·31 volts. Most benzyl bromides gave the corresponding dibenzylmercury on large scale electroreduction. p-Nitrobenzyl bromide gave 4,4′-dinitrobibenzyl while m-bromo- and 3,4-dichloro-benzyl bromides gave either the dibenzylmercury or the bibenzyl product depending on the supporting electrolyte used. Benzyl radicals are probably formed in the electrochemical rate-determining step.