Chemotherapeutic agents play an important role in cancer treatment mostly due their systemic action on human organism allowing access to liquid tumors and even metastases. Among these drugs, ruthenium compounds have been showing promising results to treat tumors and represent an important development of new antitumor therapy. This study presents the evaluation of cis-(dichloro)tetraammineruthenium(III) chloride, cis-[RuCl(2)(NH(3))(4)]Cl, genotoxic effects using human peripheral blood lymphocytes cultured in vitro. Mitotic index (MI), chromosome aberrations (CA), and DNA damage using the comet assay were analyzed. MI in human peripheral blood lymphocyte cultures treated with 1, 10, 100, and 1,000 microg mL(-1) cis-[RuCl(2)(NH(3))(4)]Cl were 5.9%, 4.6%, 3.9%, and 0%, respectively. Doxorubicin chloridate was used as the positive control. CA derived from 1, 10, and 100 microg mL(-1) concentrations were defined as spontaneous when compared with the negative control, and at the concentration of 1,000 microg mL(-1), the cell cycle was inhibited (IM = 0%). Results obtained for the comet assay using cis-[RuCl(2)(NH(3))(4)]Cl suggest that this compound has no genotoxic activity against cultured human peripheral blood lymphocytes.