In this study, six Pt(II) complexes bearing 5(6)-H or -CH3-2-phenyl or -(2'-pyridyl) or -mercaptomethylbenzimidazole ligands as,carrier groups' were synthesized and characterized by elemental analysis, IR and H-1-NMR spectra and evaluated for their preliminary in vitro cytotoxic activity to the human RD Rhabdomyosarcoma cell line and mutagenic properties in Salmonella typhimurium strains TA 98 and TA 100 in the absence of the S9 rat liver fraction. The preliminary test results showed that the complexes had slightly greater cytotoxic activity on the RD cell line at 1 muM concentration than cisplatin. Among the compounds tested for their mutagenicity, Pt(II) complexes of 2-(2'-pyridyl)- and 5(6)-methyl-2-(2'-pyridyl)benzimidazoles were found to be mutagenic. A comparative study of the MIC (minimum inhibitory concentration) values indicated that, in general, there were no differences between the poor antimicrobial activity values of the ligands and their Pt(II) complexes with respect to the tested microorganisms. These results suggest that the synthesized Pt(II) complexes should be considered for further antitumor activity studies. (C) 2003 Elsevier Science Inc. All rights reserved.