Testosterone and its metabolite 5 alpha-dihydrotestosterone (DHT) were compared with dexamethasone 21-acetate in two different animal models of arthritis and found to have effects on cartilage breakdown and inflammation. In the mouse air pouch, at the three dose levels used, significant effects were obtained with DHT and were more pronounced on cartilage breakdown than on inflammation. At the lowest dose of 0.3 mg kg-1 there was a 64% inhibition of collagen breakdown and 18% inhibition of glycosaminoglycans (GAGs) breakdown. In the antigen-induced arthritis mouse model testosterone had significant inhibitory effects on inflammation (synovial hyperplasia) and cartilage erosion.