Background: Taraxacum platycarpum has been used in traditional medicine in Korea to treat intoxication and edema and as a diuretic. According to previous reports, it has anti-cancer, anti-gastritis, and anti-inflammation effects. However, the improvement effect of T. platycarpum on rheumatoid arthritis has not been investigated. The anti-oxidative and anti-inflammation effects of the aerial parts of T. platycarpum are different from those of its subterranean parts. Thus, we evaluated the effect of the water extracts of Taraxaci radix (WTR) on type II collagen-induced rheumatoid arthritis (CIA) in animal models. Methods and Results: Rheumatoid arthritis was induced by type II collagen. WTR (100㎎/㎏ and 500㎎/㎏) was administered to the animal models. Methotrexate was used as the positive control. The levels of interleukin-6, TNF-alpha, and type II collagen IgG in the animals were measured by using enzyme-linked immunosorbent assay. Treatment with 500㎎/㎏ WTR decreased the serum levels of interleukin-6, TNF-alpha, and collagen IgG in the CIA models. Moreover, treatment with WTR diminished the arthritisinduced swelling of the hind legs and monocyte infiltration in the bloodvessels of the animal models. Conclusions: These results indicate that WTR has the potential to improve rheumatoid arthritis by reducing the levels of inflammatory cytokines such as interleukin-6 and TNF-alpha. However, further experiments are required to elucidate the influence of WTR on signal transduction in vitro and in vivo.