The redox chemistry of different nitro compounds of biological significance is focused to understand how the reduction of the nitro group can play an active role in several aspects as: electroanalytical determinations, free radical generation and stability and free radical reactivity. We have focused our studies to a lot of pharmaceuticals belonging mainly to the following families: calcium antagonists as nitrobenzene substituted 1,4-dihydropyridines, antibacterial and anti protozoan agents as nitroimidazoles and nitrofurans. The formation of the nitro radical anion as the product of the one electron reduction of nitro compounds generates a series of important consequences passing from chemical to biological aspects. We have used electrochemical techniques to study the formation, stability and reactivity of this nitro radical anion in different media. From cyclic voltammetric experiments it is possible qualitatively to visualize the formation of the nitro radical anion through the one-electron reversible couple due to the redox system nitro / nitro radical anion . Furthermore also is possible the quantitative determination of the kinetic rate constant of the nitro radical anion decay and the interaction constants with other molecules. Although substituents may affect the redox potential and consequently the stability or reactivity of the nitro radical anions, other factors are important in regulation of these properties. Among these factors, it is possible to mention the nature of the reaction media making possible the occurrence of intermolecular reactions of the father-son type between the nitro radical anion and an acidic hydrogen present in the molecules.