The aim of this study was to examine the possible clastogenic effects of trivalent chromium chloride (CrCl3) as the results in the literature are non-conclusive. Under the conditions used in this study Cr(III) induces chromosomal aberrations in phytohemagglutinin(PHA)-stimulated human lymphocytes. This activity, however, is suppressed by the antioxidants superoxide dismutase (SOD) (scavenger of O-.2), the SOD-like agents, catalase and mannitol (specific scavenger of OH.). The possibility that oxygen free radicals could evolve through stimulation of the arachidonic acid cascade is suggested using suitable inhibitors.