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The electrochemical behavior of disodium 3,3'-azobis-(6-hydroxy-)benzoate (olsalazine sodium), 2-hydroxy-5-[(4-sulfophenyl)azo]benzoic acid and 2-hydroxy-5-azo-benzoic acid was studied as a simple model of the metabolic reduction of azosalicylic acids using cyclic and square-wave voltammetry. The stability of the hydrazo intermediate generated in the electroreduction process is strongly dependent on pH and the effect of different substituents in the aromatic ring adjacent to the azo bridge. The electrode mechanism of azosalicylic acids at hanging mercury drop electrode exhibits characteristic properties of a surface redox reaction. The kinetic parameters of azo/hydrazo reduction, such as the standard redox reaction rate constant and the electron transfer coefficient were estimated applying the methods of a split SW peak and a quasireversible maximum. A sensitive analytical method for the determination of trace level of biologically active azosalicylic acids by square-wave voltammetry based on adsorptive stripping technique is described.