To study anti-coccidial infection effects of SCE, a native immunopotentiator, 1-week-old chickens (MHC; H.B15) were inoculated orally with SCE (500 mg/kg) for 3 consecutive days. Just after the final administration of SCE, chickens were inoculated orally with Eimeria tenella oocysts (NIAH strain; 2×103/chicken) for the initial infection. At 2 and 3 weeks of age, mixed antigens (0.1 ml) of sheep red blood cells (5×108) and Brucella abortus (1×109) were injected intravenously. At 4 weeks of age, oral challenge infection with oocysts (1×105/chicken) of the same strain was performed. SCE-inoculated chickens with initial infection showed an enhancement in antibody responses against both antigens. Gross and histological examinations of SCE-inoculated chickens with initial infection showed lower lesion scores and less numbers of oocysts, schizonts and gamonts in the cecum than those of any other challenged chickens. Gain/day in body weight, and hemorrhages and oocyst number in feces were also improved by SCE and/or initial infection. Taken together, these results suggest that SCE has immunostimulating and protective effects in chickens infected with Eimeria tenella oocysts. (Associate Director, Department of Production Diseases TEL +81-298-38-7780)