Osteoporosis is defined as a pathologic condition that there occurs no change in the chemical composition of the bone, while bone resorption is abnormally increased, compared with osteogenesis, leading to a decrease in bone amount. Though many varieties of therapy have been tried, no definitely effective method has been found. Ginseng saponin is an importanat component of Korean ginseng and many studies have been performed for investigating its effectiveness. But there has been no report on saponin effects to osteoporosis. The purpose of this studies is to find out the effect of saponin in osteoporosis induced by ovariectomy in rats. For the study, 30 rats underwent sham operation(group I) and 90 rats were ovariectomized. In group ll (30 rats), only ovariectomy was performed. In group III (30 rats), 50mg/kg/day ginseng saponin was administered per oral route and group IV (30 rats) was administrated 150mg/kg/day saponin. All the rats were sacrificed at the 16th week. The sections of the femoral shaft were stained using Villanueva bone stain and the sections of the tibia were stained with hematoxylin-eosin. The femoral shaft and metaphyseal region were applied to compression device for measurements of bone consistency. The effect of saponin increased weight of the femur. The cross sectional area and cortical area of the femoral shaft were significantly higher in 50mg saponin group(group III) than osteoporosis group. But there was no significant difference in the size and number of osteoclast and the percentage of trabecular bone between saponin group(group III ,IV)and osteoporosis group. In the biomechanical test, the consistency of cortical bone was significantly increased in 50mg saponin group than osteoporosis group. In conclusion, saponin had an effect on experimental osteoporosis induced by ovariectomy in rats. As though its precise mechanism was unknown, we considered that its action mechanism was due to osteoblastic activity resulting in a correction of bone mass deficit in osteoporotic rats.