The cytotoxicity and mutagenicity of three organic platinum(II) complexes 1-3 have been studied in two strains of murine lymphoma L5178Y cells. (1) [Pt(Amp)Cl] (S,N,N) (Amp, ampicillin); (2) [Pt(Met(O))Cl2] (S,N), (met(O), L-methionine sulfoxide); (3) [Pt(Met(O))(R-IDA)] (S,N) [N,N), (R-IDA, 2,4-N-(dimethylacetanilide)-iminodiacetic acid). It has been confirmed that the cytotoxic and mutagenic action of Pt-complexes depends on the structure of stable ligand and the number and structure of the leaving groups. The highest cytotoxicity and mutagenicity was found in cells treated with the dichloromethioninesulfoxideplatinum(II) complex.