This study was aimed at investigating the effects of 4-vinylcyclohexene diepoxide (VCD) on testicular tissue in dogs. For this purpose, 30 mongrel male dogs were used and allocated to 5 groups randomly. The first group (n = 6), used as the control, was administered sesame oil by the intraperitoneal route (i/p). The VCD was administered Up at doses of 80, 160, 240, 320 mg/kg to the second, third, fourth and the fifth groups (n = 6), respectively, once a day for 8 days. The dogs were surgically castrated on the day after the last VCD injection. The testes were removed immediately and fixed in 10% bovine solution. The testes were subjected to routine tissue processing and examined to determine the testicular damage in each testis. When compared to the control group, it was seen that the seminiferous tubule damage increased significantly in the treatment groups. Malondialdehyde levels reached the highest level in the fifth group, while superoxide dismutase, catalase, glutathione peroxidase activity and glutathione levels were higher in the control group (P<0.0001). Nosignificant difference was detected when all the groups were compared with respect to AST, ALT and GGT activities before and after the treatment (P>0.05). Our results showed that VCD may contribute to the sterilization of male dogs.