Effects of vanadium pentoxide (V2O5) treatment on reproductive function and testicular DNA in male mice were investigated. These functions were evaluated with fertility rate, implants, resorptions, sperm counts, motility, and morphology. The DNA damage in individual testis cells was analyzed by single-cell gel electrophoresis technique (COMET assay). V2O5 treatment resulted in a decrease in fertility rate, implantations, live fetuses, and fetal weight, and an increase in the number of resorptions/dam. Sperm count, motility, and morphology were impaired with the advancement of treatment. Vanadium treatment induced DNA damage depending on the dose in the testis cells that was expressed and detected as DNA migration in the COMET assay. The distribution of DNA migration among cells, a function of dose, revealed that the majority of cells of treated animals expressed more DNA damage than cells from control animals. It is concluded that vanadium pentoxide was a reprotoxic and genotoxic agent in mice.