Anti-infammatory, analgesic and ulcerogenic activities of fentiazac were investigated in comparison with those of acetylsalicylic acid, fenbufen, naproxen and phenylbutazone. On the anti-inflammatory activity in carrageenin-induced rat paw edema and the analgesic activity on writhing syndrome induced with acetic acid in mice, fentiazac displayed more potent effect than acetylsalicylic acid, fenbufen and pbenylbutazone. But the ulcerogenic action of fentiazac on gastrointestinal tract in fasting rats was less than that of reference drugs. From these investigation, fentiazac seemed to indicate a poor correlation between the extent of anti-inflammatory activity and ulcerogenic action.