Potential carcinogenicity of some transition metal ions was tested using a direct-current polarography method. The measurements were based on the reduction of tested compounds in an anhydrous solution using alpha-lipoic acid as the detection compound. The potential carcinogenicity was expressed in terms of the parameter tg alpha, which is known to directly correlate with the carcinogenicity of tested compounds. For the metal ions tested, tg alpha was found to decrease in the following sequence: Fe(III) > Pb(II) > V(IV) > Fe(II) > Mn(II) > Cu(II). Zero values of tg alpha were found for Cd(II) and Mn(III).