Glucosamine (CAS 3416-24-8) is an aminomonosaccharide naturally occurring in the human body. It was tested for antiinflammatory activities and it showed to protect against the edema provoked in the rat paw by carrageenin, dextran, formalin, but not against the edema provoked by specific inflammation mediators, such as bradykinin, serotonin, histamine. Glucosamine protected against pleurities provoked in the rat by carrageenin, but not against that provoked by bradykinin. Furthermore glucosamine protected against peritonitis provoked in the rat by formalin and in the mouse by acetic acid. Glucosamine did not show antinoceptive properties against writings provoked by i.p. phenylquinone in the mouse. Glucosamine did not show inhibiting activities on cyclooxygenase or on the proteolytic enzymes in the inflamed paw of the rat, but it was able to inhibit in vitro superoxide generation and lysosomial enzymes of the liver. The potency of glucosamine on the antiinflammatory tests was lower than that of acetylsalicylic acid and much lower than that of indomethacin. Its acute toxicity, however, and notably the toxicity on the gastrointestinal tract is very low, practically absent. The pharmacological therapeutic index of glucosamine with regard to the antiinflammatory activities seems therefore comparable or superior to that of the known non-steroidal anti-inflammatories.