Recently many efforts were focused to understand the mechanical insights of melanogenesis to develop the agents for hyper-pigmentation and hypo-pigmentation. In the melanin biosynthetic pathway, tyrosinase is the rate limiting enzyme, and α-melanocyte stimulating hormone(MSH) stimulate melanogenesis and enhance the melanin synthesis and the tyrosinase activity. This study the effects of Radix Trichosanthis on the basal melanogenic activities of B16/F10 mouse melanoma cells, and on the α-MSH induced melanogenesis. Radix Trichosanthis alone markedly suppressed melanin content and tyrosinase activity in a dose-dependent manner. Pretreatment of the cells with Radix Trichosanthis also suppressed the increase of α-MSH (10 nM) induced melanin content and tyrosinase activity. These results suggest that Radix Trichosanthis inhibits melanogenesis and abrogates α-MSH induced melanogenesis in B16 melanoma cells.