This study was performed to investigate the effects of exposure to vincristine (VCR) alone (1 mg kg^-1 or 2 mg kg^-1) and in combination with X-rays (0.25 Gy + 1 mg kg^-1 VCR or 1.00 Gy + 2 mg kg^-1 VCR) on the quality and quantity of spermatozoa, and the offspring of exposed Pzh : Sfis male mice. Both VCR and X-rays plus VCR reduced testis weight and sperm count, caused deterioration with respect to sperm morphology, and caused a slight increase in DNA damage. Exposure of some stages of male germ cells to high doses of VCR either alone or in combination with X-rays reduced the rate of pregnant females and the fertility of males. Such treatments reduced the number of total and live implantations, and induced dominant lethal mutations. The results of this study demonstrated the reproductive genotoxicity of VCR with or without X-rays, but did not unequivocally confirm their ability to cause external malformations in offspring.