Abstract: The percutaneous penetration of ~3H-huangbai extracts and ~3H-berberine through excised guinea pig and human shins was studied using the static diffusion cell technique. The data were treated with mathematical model of skin absorption. The results showed that huangbai extracts and berberine could penetrate the guinea pig and human skins at (above) dose of 8.38 ug/cm~2 and 14.32 ug/cm~2, respectively. The amount and rate of penetration increased linearly with the time of exposure and dose. The permeability of berberine through guinea pig and human skins in two vehicles (water and glycol) was lower than that of huangbai extracts. When Huangbai extracts and berberine were applied in glycol solution, the vehicle greatly enhanced the penetration of the two penetrants. It was found that K_p(perme ability constant) of two penetrants through two kinds of skin decreased in following order: K_p of huangbai in glycol through guinea pig skin >K_p of huangbai in water through guinea pig skin >K_p of huangbai in water through human skin >K_p of berberine in glycol through guinea pig skin >K_p of berberine in water through human skin. The lag time of two penetrants through human skin was longer than that through guinea pig skin.