The effects of vanadium-pentoxide (1314621) (V2O5) on mitosis, sister chromatid exchange (SCE), micronucleus formation, and gene mutation at the HPRT locus in the V79-Chinese-hamster cell line were determined. Cytotoxicity was measured by cell cycle kinetic data based on the number of mononucleated and binucleated cells in the presence of cytochalasin-B after 24 hours (hr) of treatment with V2O5 at 1 to 12 micrograms/milliliter (microg/ml). Micronucleus formation in V79 cells was assessed after treatment with V2O5 at 1 to 3microg/ml for 24hr, after which the cells were stained with antikinetochore antibodies. SCE was assessed in V79 cells after treatment with V2O5 at 1 to 4microg/ml for 24hr, after which they were stained using the fluorescent Giemsa method, and counted for replicative index and SCE. The ability of V2O5 to induce gene mutations at the HPRT locus in V79 cells was studied after V79 cells were incubated with V2O5 for 24hr, and then subcultured in the presence of 6-thioguanine to look for colony forming efficiency. The results indicated that there were no significant increases in the frequency of SCE or gene mutations after V2O5 treatment of V79 cells. There was a dose related increase in the number of micronucleated cells in V79 cells in culture that were kinetochore positive, and the number of binucleated cells after cytochalasin-B treatment decreased with increased V2O5 dose. The authors conclude that V2O5 induced micronuclei are due to spindle dysfunction, and that V2O5 is aneuploidogenic in V79 cells.