---

Background and Objective: Para-nonylphen as an environmental pollutant has weak estrogenic activity and causes oxidative stress in different organs including testis. This study was done to determine the protective effect of vitamin E on the para-nonylphenol induced-testicular toxicity in adult rats. Methods: In this experimental study, 24 Wistar rats were randomly allocated into four groups including control, vitamin E (100 mg/kg/day, orally), para-nonylphenol (250mg/kg/day, orally) and finally para-nonylphenol (250mg/kg/day, orally) plus vitamin E (100mg/kg/day, orally). After 56 days of treatment, removal of the right testis, tissue processing and staining with Heidenhain's Azan, the morphometric parameters of testicular tissue was evaluated using stereological method. Results: The mean volume of seminiferous tubules, height of the germinal epithelium, seminiferous tubules diameter, thickness of the basement membrane, number of spermatocyte, spermatid and sertoli cells significantly reduced in para nonylphenol group compared to the controls (P<0.05). These parameters were significantly increased in the para-nonylphenol plus vitamin E group compared to para nonylphenol group (P<0.05). In the histopathological examination, atrophy of seminiferous tubules, germinal epithelium vacuolation and epithelial disarrangement were observed in para nonylphenol group. Histopathological alterations reduced in para-nonylphenol plus vitamin E group compared to para nonylphenol group. Conclusion: Co-administration of vitamin E with para nonylphenol can prevent the adverse effects of para nonylphenol on the testicular tissue in adult rats.