2,6-Diamino-1,4-dihydropyridines bearing carbonyl functions in the 3- and 5-positions and being substituted in the 4-position by lower alkyl, phenyl, substituted phenyl or a heterocyclic group are antihypertensive agents and coronary vessel dilators. The compounds, of which 2,6-diamino-4-(3-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylic acid 3,5-diethyl ester is a representative embodiment, are prepared through condensation of an amidine with either an aldehyde or an ylidenecyanoacetoacetic acid ester.