Melanogenesis is a well known physiological response of human skin exposed to ultraviolet light, genetic reasons and other sources. In this study, we conducted to evaluate the effects of Radix Ginseng (RG) and Radix Trichosanthis (RT) on the melanogenesis in the B16 melanoma cells. The cells were treated for 48 h with RT at concentrations ranging from 1 to 50 microg/ml, RG at concentration of 10-1000 microg/ml, or RG at various doses (10-1000 microg/ml) with 25 microg/ml RT. Treatment with RT alone dose-dependently suppressed tyrosinase activity and melanin content compared with untreated control, and significantly inhibited cell proliferation. However, RG at various concentrations did not exhibit any significant change of them. Treatment with RT in the presence of various concentrations of RG suppressed tyrosinase activity and melanin content, similar to treatment with RT alone, but slightly increased cell proliferation. Furthermore, tyrosinase protein level was significantly decreased in treatment with 25 microg/ml RT alone and with a combination of 100 microg/ml RG. These results indicate that treatment with RG and RT significantly inhibits the melanogenesis in B16 cells, and raise the possibility that this combination may be effective in the whitening agent for the skin.