Abstract: Objective To assess the toxicity of nickel sulfate(NiSO₄) on the testes of male rats.Methods The Wistar rats were treated with various concentrations of NiSO₄ (0,1.25,2.50,and 5.00 mg/kg/day) for 30 days.Then,sperm motility,reactive oxygen species(ROS) in testicular cells,and the expression of Bax and caspase-3 protein were detected.Results Significant decreases in sperm motility and density of spermatozoa(ρ) in the 2.50 and 5.00 mg NiSO₄ groups were observed compared with the control group(P< 0.05).In contrast,intratestiular ROS and the expression of Bax were increased in 2.50 and 5.00 mg NiSO₄ groups compared with the controls (P< 0.01).At the same time,pro-caspase-3 protein increased significantly and cleaved-caspase-3 protein expression occured in all NiSO₄ exposure groups.Furthermore,the expression of cleaved-caspase-3 protein increased in a dose-dependent manner in all NiSO₄ groups.Conclusion NiSO₄ at concentrations of 2.50 and 5.00 mg exhibits reproductive toxicity in rats by decreasing sperm.Furthermore,intratesticular ROS,Bax,pro-caspase-3 and cleaved-caspase-3 overexpression play pivotal roles in reproductive damage induced by NiSO₄.