The anti-inflammatory effects of etodolac (Eto) were compared with those of 6 other anti-inflammatory drugs : indomethacin (Ind), diclofenac Na (Dic), piroxicam (Pir), naproxen (Nap), ketoprofen (Ket) and aspirin (Asp). Eto inhibited carrageenin-induced edema in rats, adjuvant-induced arthritis in rats, acetic acid-induced writhing in mice and brewer's yeast-induced hyperalgesia and fever in rats. In the adjuvant arthritis test, the ED₃₀ value (1.88mg/kg) on day 3 and ED₅₀ values (adjuvant-injected paw : 1.18mg/kg and non-injected paw : 0.96mg/kg) on day 18 for Eto were comparable to those for Dic (2.16, 1.72 and 1.28) when given prophylactically and the ED₅₀ values for Eto (adjuvant-injected paw : 1.61 and non-injected paw : 1.20mg/kg) were comparable to those for Ket (1.24 and 1.22) when used therapeutically. The analgesic activity of Eto (ED₅₀ value : 3.67mg/kg) in the acetic acid-induced writhing test was greater than that of Nap (9.83) or Asp (31.6) and less than that of Ind (0.71), Dic (1.54), Pir (0.92) or Ket (1.34). In the antipyretic test, the minimum effective dose (MED : 1mg/kg) for Eto was comparable to that for Ind (1.0), Nap (1.0) or Ket (1.0). Eto was less potent in inhibiting carrageenin-induced edema (ED₃₀ value : 6.99mg/kg) and inflammatory pain (ED₅₀ value : 9.24mg/kg) than the other drugs (Ind : 2.32 and 3.47, Dic : 0.69 and 3.80, Pir : 1.31 and 1.94, Nap : 1.83 and 2.78, Ket : 1.12 and 0.63), except for Asp (167 and 51.8). Eto was the least ulcerogenic (UD₅₀ value : the dose which caused ulcer action in 50% rats : 84.2mg/kg) compound among the drugs tested (Ind : 4.24, Dic : 12.7, Pir : 3.14, Nap : 42.3, Ket : 2.69, Asp : 20.8), so its safety margin (the ratio of the UD₅₀ value to the ED₃₀, ED₅₀ or MED value) was greater than those of the other drugs. Thus, Eto is considered to be an effective anti-inflammatory drug with weak ulcerogenic activity.