To determine the effect of Pueraria mirifica (PM) on serum parathyroid hormone (PTH) and calcium levels on aged menopausal monkeys (Macaca fascicularis), subjects were treated with 10, 100, or 1,000 mg/day of PM. Blood samples were collected every 5 days for 30,90, and 60 days during pretreatment, treatment, and post-treatment periods, respectively. Sera were assayed for PTH, estradiol, and calcium levels. PM-1,000 had the strongest effect on the decrease in PTH (0.001<P <= 0.05) and calcium levels (0.001<P< 0.03) during the treatment period. PTH levels remained low for the first 15 days of the post-treatment period (0.01:<Pless than or equal to0.05). PM-10 induced a significant decrease in PTH level on day 80 (P=0.02) during the treatment period and a significant decrease in calcium level on day 75 (P<0.01). There were no changes in serum PTH and calcium levels throughout the study period in the PM-100 group. Estradiol levels decreased significantly during the treatment period in all treatment groups. The results suggest that long-term treatment with 1,000 mg/day of PM decreases serum PTH and calcium in aged menopausal monkeys, indicating that PM ameliorates bone loss caused by estrogen deficiency.