The polarographic reduction of 1, 4-dihydropyridine-3, 5-dicarboxylic acid derivatives in dimethylformamide was studied. It is shown that the first diffusion waves of these compounds are irreversible one-electron waves and correspond to electrical reduction of the C=C bond of the conjugated system of the 1, 4-dihydropyridine ring to give a tetrahydro derivative. In the case of pyridine-3, 5-dicarboxylic acid esters partial dimerization of the resulting freeradical products occurs along with electron transfer. It is shown that the introduction of alkoxycarbonyl substituents in 2, 6-methyl and 3, 5-methoxycarbonyl groups and in the 4 position and of a carboxyl group in the 4 position facilitates the electrical reduction of the 1, 4-dihydropyridine ring. The introduction of a methyl group in the 4 position hinders reduction of the ring.