Ketoprofen possesses the typical pharmacological properties of non-steroidal anti-inflammatory agents i.e. anti-inflammatory, analgesic and antipyretic activity, as well as antibradykinin activity and ability to inhibit prostaglandin synthesis. Ketoprofen is as potent as indomethacin in the tests for anti-inflammatory and analgesic activity, but its antipyretic and antibradykinin activities and its inhibitory activity against prostaglandin synthesis is respectively 4, 8 and 8 times greater than that of indomethacin. It seems very likely that the pituitary-adrenal axis is not involved in the mechanism of the anti-inflammatory action of ketoprofen, since in the carrageenan abscess test, the compound shows the same activity both in adrenalectomized and in normal rats and, when locally applied to the inflamed area, it is more active than when administered systemically. In the mouse the acute oral toxicity of ketoprofen is about one twentieth that of indomethacin. Like all powerful steroidal or non-steroidal antiinflammatory agents, ketoprofen shows some gastrointestinal toxicity, but its effect is mild and distinctly less than that of indomethacin. Pharmacokinetic studies in the rat, dog and monkey have shown that gastro-intestinal absorption of the drug is rapid and almost complete; the compound and its metabolites are excreted from the body fairly rapidly.