It was attempted to observe the effects of ginseng saponin, one of the major components of Korean Panax ginseng (C, A, Meyer) roots, on cholesterol transport and androgen biosynthesis in vivo as well as in vitro, and the following results were obtained. 1. Ginseng saponin was adminstered by stomach tubing prior to intraperitoneal injection of (4-^(14)C)-cholesterol into adult male rats, They were sacrificed from 1 hr to 24 hr after the injection of cholesterol. The tissue samples were homogenated, extracted and counted, 2. The first high radioactivity of the liver of test animal was observed 6 hr after radioactive cholesterol injection. However, that of control appeared at 12 hr after the injection, 3. The first high radioactivity in blood serum of the test group appeared at 6 hr after radioactive cholesterol injection, while that of control group at 16 hr after the injection, 4. The first high radioactivity of the test rats was observed between 4 and 6 hr after radioactivity peak at 12 hr. 5. The effect of ginseng saponin on androgen biosynthesis in vitro by the rat testis homogenate was investigated, It was found that the degree of cholesterol transformation into androstendione and testosteron of test was much higher than that of control, suggesting that the ginseng saponin stimulated the biosynthesis of androgens.