The electroreduction of a series of nitroaryl-1,4-dihydropyridines has been studied in mixed media. Controlled potential electrolyses using a mercury pool electrode at three different reduction potentials were carried out. Voltammetric (polarography and cyclic voltammetry) and chromatographic studies, showed that these nitro compounds were transformed into their corresponding hydroxylamine derivatives at the end of the electrolysis. On the other hand, early in the electrolysis it was possible to detect the formation of the nitro radical anion in the bulk solution which through a dismutation reaction produces the nitroso compound which is reduced to the final product, a hydroxylamine derivative. When different biomolecules like glutathione, cysteamine, adenine, and uracil were added, a direct reaction with the nitro radical anion derivative was detected. The parent nitro compound and the final product, the hydroxylamine derivative, did not react with the biomolecules.