Glucosamine is an aminomonosaccharide naturally occurring in the human body. It was tested for anti-inflammatory activities and it showed to protect against the edema provoked in the rat paw by carrageenin, dextran, and formalin, but not against the edema provoked by specific inflammation mediators, such as bradykinin, serotonin, and 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 writhings provoked by i.p. phenylquinone in the mouse. It also 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 anti-inflammatory tests was lower than that of acetylsalicylic cid and much lower than that of indometacin. 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 anti-inflammatory activities seems therefore comparable or superior to that of the known NSAID's.