The electrochemical behavior of mixed monolayers of N-tetradecyl-N＇-methyl viologen (TMV) and L-alpha-dimyristoylphosphatidic acid (DMPA) has been studied. Mixed monolayers of TMV/DMPA = 1:2 have been obtained at the air-water interface and transferred by the Langmuir-Blodgett (LB) method at pi = 40 mN m(-1) onto In and Sn oxide (ITO) electrodes. These LB films were used as the working electrode in a conventional electrochemical cell and immersed in aqueous solutions with different electrolytes. The influence of the type and the electrolyte concentration on the voltammetric peaks related to the two one-electron processes of TMV has been studied. The formation of an insoluble salt of viologen perchlorate on the surface of the electrode is observed when concentrations of perchlorate higher than 0.3 M are used. Due to this, a reorientation of the polar group of the viologen in the transferred mixed monolayer from a flat to a perpendicular position is postulated.