BACKGROUND: The purpose of this study was to investigate the effect of chronic uptake of bhang, prepared from the Cannabis sativa, on male reproductive physiology in adult male Parkes strain (P) mice. An attempt was also made to investigate the presence of cannabinoid 1 (CB1) and cannabinoid 2 (CB2) receptors, and fatty acid amide hydrolase (FAAH) in the testis and to evaluate any changes in it resulting from chronic intake of bhang in mice. METHODS AND RESULTS: Adult male mice were given bhang (3 or 6 mg/kg body weight/day) orally for 36 consecutive days. Chronic intake of bhang caused regressive changes in the testes and suppressed sperm count, viability and motility. Bhang intake also caused significant decline in circulating testosterone level due to decline in testicular 3β HSD enzyme activity. An immunohistochemical study demonstrated the presence of CB1, CB2 and FAAH in the testis of mice. The present study also showed significant variation in the CB1 and CB2 receptors and FAAH protein levels in testes of mice exposed to bhang. These suppressive effects may be due to inhibitory effect of bhang on pituitary expression of gonadotrophin releasing hormone (GnRH) I receptor protein. Treatment of testes with bhang in vitro significantly decreased testicular luteinizing hormone receptor (LHR) and FAAH expression suggesting direct action of bhang on testicular activity. CONCLUSIONS: The findings of this study thus suggest that bhang may impair fertility in male mice through alteration in the testicular endocannabinoid system and that chronic bhang exposure in humans would be predicted to alter male fertility. Birth Defects Res (Part B) 92:195–205, 2011. © 2011 Wiley-Liss, Inc.