A sensitive and selective method for the simultaneous determination of lead, cadmium and zinc based on the formation of their complexes with Clioquinol (5-chloro-7-iodo-8-hydroxyquinoline, CQ) is described. These studies were carried out using separate copper, lead, cadmium and zinc solutions and also mix- tures of them. The optimum pH values were 2.3; 5.1; 5.3 and 5.2 for copper, lead, cadmium and zinc respectively (Britton Robinson buffer 0.03 mol L