The effects of Na[trans-RuCl4(DMSO)Im] (NAMI), Na[trans-RuCl4(TMSO) Ind] (TIND) and Na[trans-RuCl4(TMSO)Iq] TEQU) were tested in vitro on TLX5 lymphoma cells in comparison to cisplatin by means of the sulforhodamine-B test SRB) for protein content determination, by acridine orange and propidium iodide staining and by means of the bromodeoxyuridine test, for cell cycle modifications. After 1 h drug exposure with metal-based drugs, TLX5 lymphoma cells require a further 72 h in vitro cultivation to show alteration of cell cycle. Ruthenium compounds show a different pattern of effects: TEQU causes the same dose-dependent cytotoxicity and DNA fragmentation shown by cisplatin, TIND reduces absorbance with the SRB test and slightly increases S and G2M populations with a time-dependent drug exposure of tumour cells, and NAMI is virtually devoid of any detectable effect. By in vivo bioassay of in vitro treated tumour cells, TIND and TEQU are effective independently of the time of drug exposure of tumour cells, this effect being confirmed by the same cell uptake of ruthenium after 1 or 4 h treatment, determined by atomic absorption spectroscopy. These data stress the lack of the involvement of direct cytotoxic effects in the potent anti-metastatic action of NAMI.