Infrared therapy has been used widely in the treatment of many painful conditions, burns, contractures, and inflammatory processes, etc. But, its effect on rheumatoid arthritis has not been studied much. In animal models of experimental arthritis, Type II collagen induced arthritis is similar to rheumatoid arthritis in pathophysiological, clinical and immunological aspects. We made arthritis in 32 rats by intradermal injection of type II collagen, and treated them with infrared irradiation. The therapeutic effect was followed by measuring arthritis index, radiologic index, and intermalleolar distance. The results showed no significant change between before and after treatment. Also, no significant difference was observed between control and treatment groups.