The pathological effects of orchidectomy on intestine tissue and serum level of carcino embryogenic antigen S. Sattari * , R. Ahmadi * Azad University of Iran, Science Dept., Hamedan, Iran Objective: Carcino Embryogenic Antigen (CEA) is a wellknown tumor marker influenced by carcinogenic changes in intestine tissue. The purpose of this study was to determine the effects of orchidectomy on serum level of CEA and histological changes of intestine in male rats. Method: Male Wistar rats were randomly divided to control, sham, uni-orchidetomised and biorchidectomised groups of 5 in each. 10 weeks after operation, blood samples were collected using cardiac puncture method. Serum CEA level was measured using ELISA method. The effect of orchidectomy on intestine tissue was also histologically studied. The results were statistically analyzed using ANOVA. Results: Serum level of CEA was significantly increased in orchidectomised rats compared with control animals (P< 0.001). The increase in serum CEA level was more in biorchidectomised than uniorchidectomised rats (P<0.001).