The remarkable insights into the pathogenesis of osteo-arthrosis (OA) have also affected the therapeutic field. Efforts have been made to find drugs which would somehow block or slow down the evolution of this disease. In this connection, a major contribution has been made by the investigations on glycosaminoglycans (GAGs), which play a crucial role in the physiology of joint cartilage. It was thus suggested that proper supplementation with GAGs might enable chondrocytes to replace the proteoglycans (PG). Galactosaminoglucuronoglycan sulfate (GAGGS) has been used for this purpose. In preliminary clinical trials, GAGGS exhibited a remarkable tolerability and good therapeutic efficacy. GAGs are generally able to inhibit certain enzymes present in the synovial fluid which may damage joint cartilage (elastase, hyaluronidase). Moreover, GAGGS has also been shown to act as an anti-inflammatory drug since it has an inhibitory effect over the complement. All these data supply evidence that, in theory, GAGGS may have a chondroprotective effect in patients with OA. In addition to the positive results of preliminary clinical trials, the use of GAGGS in OA therapy is based on the fact that this drug is absorbed by the body, is concentrated in the cartilages and produces no toxic or teratogenic effects. In the clinical studies performed so far, although of the open type, GAGGS has always yielded clinical improvement both of painful symptoms and of limited function thanks to its proven anti-inflammatory activity. Thus once the results from other ongoing trials (double blind) are available, hopefully GAGGS will in fact become a basic drug for OA therapy.