The possibility of using mice in place of rats on the anti-inflammatory screening tests was investigated. The diversities of the responses between mice and rats on screening tests, that is, carrageenin, formalin-induced edema in the hind paw, adjuvant arthritis and cotton pellet granuloma were observed with p.o. administration of prednisolone, 0.5 mg/kg and 5.0 mg/kg, and indomethacin, 0.5 mg/g and 5.0 mg/kg. On the effect of these drugs on screening tests, a similar type of phenomena between rats and mice was found. Then the close-response relationships of aspirin, flufenamic acid, phenylbutazone, cyproheptadine, prednisolone and indomethacin were examined in four kinds of screening tests mentioned above. Prednisolone, indomethacin, phenylbutazone and aspirin inhibited the carrageenin, formalin-induced edema, cotton pellet granuloma and adjuvant arthritis apparently, but flufenamic acid showed no inhibition on the carrageenin and formalin-induced edema. Cyproheptadine inhibited the formalin and serotonin-induced edema. We have found that mice, instead of rats, can be used for the anti-inflammatory screening methods.