In the present paper the antiprotozoan activity of several rhodium(III) complexes was studied by analysis of the [3H]-thymidine, [3H]-uridine and [3H]-leucine uptake occurring in epimastigotes of Trypanosoma cruzi in the presence of the drug as well as their effect on the viability and motility of infective forms. It has been found that the complexes do not interact with native DNA but that some of them inhibit both the precursor uptake and the viability of metacyclic forms. It seems that the mode of action on the epimastigotes should be different from that observed on metacyclic forms.