Objective: Treatment with cyclophosphamide (CP) a commonly used anticancer and immunosuppressive agent may result in oligospermia and azoospermia. CP administration induces oxidative stress and is cytotoxic to normal cells. In this context we have studied the CP induced oxidative injury in rat sperm. Materials and Methods: Animals were randomly divided into two groups comprised of 8 animals in each. Treatment groups were as follow: group 1 received distilled water by oral gavage daily and group 2 received CP (6 mg/kg/day) dissolved in distilled water by gavage. The groups were treated for 4 weeks. The protocol for this study including doses and duration of treatment for CP were all designed according to previous studies.At the end of the specified treatment the samples of plasma testes and epididymides were collected for the analysis of free radical toxic stress markers including cellular lipid peroxidation (LPO) and total antioxidant power (TAP) and histopathological study. Results: The testes of CP-exposed rats showed a significant increase in lipid peroxidation along with a significant decrease in total antioxidant power. Histopathological assessment of sperm concentration performed on cauda epididymis sections from CP-treated animals showed severe decrease of mature spermatozoa concentration in lumen. Histopathological examination of testis sections revealed inhibition of spermatogenesis and the preferential loss of maturing and elongated spermatids. qualitative examination of testicular sections revealed fewer mature luminal spermatozoa in comparison to the control. In CP-treated animals there was seen disorganized germ cells epithelium in the most of seminiferous tubules along with degenerated and necrotic cells in some of seminiferus tubules. In some section of seminiferous tubules large number of metaphasic cells in germ epithelium was observed. Conclusion: Cyclophosphamide treatment at the dosage used caused testicular gametogenic disorders and arrest of sperm maturation via induction of oxidative stress.