This study was designed to investigate the effects of caffeine intake on Ca and P metabolism in ovariectomized rats. For this purpose, the ovariectomized female rats weighing 230.8$pm$3.5g were divided into four groups, eight rats each ; control, low caffeine(LC), medium caffeine(MC)and high caffeine(HC) groups. They were supplied for six weeks with the caffeine of 0mg, 66.8mg, 167mg and 334mg per kilogram of diet, respectively, and the results are summarized as follows. 1) There were no significant differences in feed intake, feed efficiency ratio and body weight change among all of experimental groups. But liver weight(both total weight and weight/body weight) was significantly decreased by caffeine in MC group. 2) The weight of tibia was decreased by caffeine intake in MC and HC groups. But the length, Ca and P content of tibia and femur was not changed in all of caffeine groups. 3) Ca, PTH and calcitonin levels in serum were not affected by caffeine. While, serum P level in HC group was significantly increased as compared with the control. 4) The fecal excretion of Ca and P tended to be higher in the caffeine groups, and as the result, the absorption rate, retention and retention rate of Ca and P tended to be decreased. It was noteworthy that P retention was significantly lowered in HC group as compared with LC group. The results showed that, when caffeine was taken by ovarietomized rats, the weight of tibia was decreased and the retention rate of Ca and P tended to be lowered. Therefore, too much intake of caffeine for women whose bone mineral density of tibia is decreased after postmenopause seems to accelerate the decrease of bone mineral density due to the negative effect on metabolism of Ca and P.