Four Pt(II) complexes with 2-H/or-methyl/or-aminomethylbenzimidazole or 1,2-dimethylbenzimidazole ligands as "non-leaving groups" were synthesized and their antiproliferative properties were tested against the human MCF-7 breast cancer cell line. The mutagenic potentials of the complexes were tested in Salmonella typhimurium strains TA 98 and TA 100 in the absence of S9 rat liver fraction. In general, Pt(II) complexes tested which were found to be less active than cisplatin, exhibited moderate in vitro cytotoxic activity on MCF-7 cell line. Among the complexes tested, Pt(II) complex with 2-aminomethylbenzimidazole ligand was found to be highly mutagenic in S. typhimurium TA 98 and low mutagenic in S. typhimurium TA 100. Pt(II) complex with 1,2-dimethylbenzimidazole was mutagenic only in S. typhimurium TA 98. The other two complexes were found to be non-mutagen in both strains. (C) 2003 Editions scientifiques et medicales Elsevier SAS. All rights reserved.