Abstract: OBJECTIVE To investigate the antipyretic, analgesic and anti-inflammatory effects of nimesulide in laboratory animals, and compare the ED50 of three pharmacological activities. METHODS The antipyretic activity was evidenced by heat inactivation E. coli induced fever in rabbits; the analgesic activity was evidenced by acetic acid induced abdominal pain in mice; the anti-inflammatory activity of nimsulide was evidenced by carrageenan induced paw edema in rats. RESULTS In the antipyretic test to lower body temperature by heat inactivation E. coli induced fever, the ED₅₀ was 0.85-1.95 mg·kg^?1 within 2-6 h. In anti-analgesic studies using writhing test in mice, the ED₅₀ was 24.56 mg·kg^?1. The ED50 of nimesulide p.o. were determined in carrageenan foot edema in rats within 1-7 h, ED₅₀ was 3.15-4.05 mg·kg-1. The median effective doses in animals were converted to the ED₅₀ in human being were 0.50-0.60, 2.72, 0.26-0.59 mg·kg-1, respectively. CONCLUSION The various pharmacological activities ED50 of nimesulide is different, the effective dose of antipyretic is the lowest.