In order to investigate the effect of the oral administration of Guirokyisun-Hwan on the estrogen-deficiency osteoporosis induced by ovariectomy in the rats, serum osteocalcin, estradiol, progesterone, follicular-stimulating hormone (FSH), calcium (Ca) and phosphorous (P) levels were monitored. And body weight changes were also monitored throughout whole experimental periods. The results were as follows : 1. Body weight of Control and Treatment group was significantly increased from 6 weeks after ovariectomy but after 2 days of drug administration, body weight of Treatment group were significantly (p<0.01 or 0.05) decreased compared with those of Control group. 2. Serum osteocalcin levels were significantly (p<0.01) increased in control groups compared with those of Sham group but significantly (p<0.01) decreased in the Treatment group. 3. Serum estradiol levels were significantly (p<0.01) decreased in control groups compared with those of Sham group but significantly (p<0.01) increased in the Treatment group. 4. Serum progesterone levels were significantly (p<0.01) decreased in control groups compared with those of Sham group but significantly (p<0.01) decreased in the Treatment groups. 5. Serum FSH levels were significantly (p<0.01) increased in control groups compared with those of Sham group but significantly (p<0.05) decreased in the Treatment group. 6. Serum Ca levels were significantly (p<0.01) decreased in control groups compared with those of Sham group but significantly (p<0.01) increased in the Treatment group. 7. Serum P levels were significantly (p<0.01) increased in control groups compared with those of Sham group and Treatment group. No significant was detected between Control group and Treatment group. According to these results, it is considered that the oral administration of Guirokyisun-Hwan have favorable effect on treatment and prevention of osteoporosis induced by ovariectomy in rats.