Electroreduction of pyridinedicarboxylic acid derivatives 1a–g in methanol containing ammonium chloride using a divided cell brought about highly selective hydrogenation to give the corresponding dihydropyridines in good yields. From the electrolysis of dimethyl 2, 3-and 2, 5-pyridinedicarboxylates 1a, c, only the corresponding 1, 2-dihydropyridine derivatives 2a, c were obtained in a regioselective manner while that of 2, 4-, 2, 6-, and 3, ...