Smilax china L. rhizome extract(SCE), called ``Tobokreung`` in Korean traditional medicine was investigated the influence on heavy metal contents(particularly Pb, Cd, As, and Hg) in Sprague-Dawley rats for 3 weeks. The test groups were divided into 4 group, normal, control, and SCE feeding groups, SC1(13 ㎎/㎏) and SC2(26 ㎎/㎏), respectively. The three group except normal group, were fed heavy metal such as Pb, Cd, As, and Hg. Body weight gain and the weight of target organs (liver and kidney) were determined and had not shown significant differences. Pb, Cd, and As contents in the kidney of SCE feeding groups were tended to decrease after 3 weeks, and SC2 group showed remarkably decrease of them. In the liver, the 3 heavy metal contents except Cd of SC2 group, were decreased rather than that of control group. Pb contents in the serum and the hair of the SC2 group showed significantly decreasing. All the taken together, we investigated the effect of SCE on the 4 heavy metal contents in rats for 3 weeks, and found out that more dosage of SCE made lower heavy metal contents in vivo, for the first time.