The authors present a review of the mechanisms of free radicals production and report the results of "in vivo" and "in vitro" studies correlating these agent with the physiopathologic changes of the rheumatoid arthritis. The data reviewed in this paper support the idea of the participation of free radicals in the articular lesion. However new studies are necessary to determine the contribution of free radicals on disease development, chronicity and the efficacy of antioxidant agents.