Interactions of cadmiumand lead metals with promazine were investigated by Differential pulse voltammetry. Measurements were performed in sodium acetate buffer at pH 6.00 in aqueous solutions under physiological ionic strength (0.15 mol dm-3). The electrochemical behavior of complexes of Cd (II) and Pb (II) with promazine were studied for determination of the corresponding stability constants ([M2+] = 9ï´10-5mol dm-3, pH= 6.00; total concentration of promazine from1ï´10-5 to 1ï´10-4mol dm-3). Itwas observed that promazine forms 1:1 and 1:2 complexeswith Cd (II) and Pb (II) respectively. The stability constants of the Cd (II)-promazine and Pb (II)-promazine complexes were evaluated with the DeFord-Hume procedure at different ligand concentrations and they were calculated fromthe dependence of the shift ofmetal peak potential on the free promazine ion concentration.