Fifty-four outpatients with gonarthrosis participated in a double-blind clinical test with the aim of evaluating the efficacy and tolerance of intra-articular glucosamine in comparison with a 0.9% NaCl placebo. Each patient had 1 I.A. injection per week for 5 consecutive weeks. Pain, active and passive mobility of the joint, swelling, and generalized and local intolerance symptoms were recorded before treatment and 4 weeks after the last injection. Glucosamine significantly reduced pain and resulted in more pain-free patients then did the placebo. Joint flexibility also increased substantially vs. the placebo while active mobility increased with both but more so with the Glucosamine. Glucosamine administration was able to accelerate the recovery of arthrosis patients, with no resulting side effects, and to partially restore articular function. In addition, the clinical recovery did not fade after treatment ended, but lasted for the following month, at least. These features are a definite improvement ovr antirheumatic drugs, the major drawbacks of which are action of short duration and side effects. Glucosamine therapy therefore deserves a selected place in the management of osteoarthrosis.