This study was performed to investigate the effect of dietary protein level on the metabolic changes of Ca and skeletons in postmenopausal women, using ovariecotomized rats as an animal model. The female rats of 200∼250g were fed either 8%(L) or 50%(H) casein diet for 15 weeks(1st experiment). At 15th week, the rats of each diet group were undergone ovariectomy or sham-operation and they were continued to feed the same experimantal diet for 9 more months(2nd experiment). Ca metabolism, kidney function and bone composition were determined at the end of 1st experiment, 3rd and 9th month of 2nd experiment. After 1st experiment, high protein group showed higher urinary Ca and protein excretion, however, there was no difference in GFR and urinary hydroxyproline excretion. The weights, ash and Ca content of femur, scapular and vertebra tended to be higher in high protein groups which tells that high protein promoted skeletal growth. In 2nd experiment, high protein group showed higher urinary Ca and protein excretion and lower Ca absorption and balance. GFR was not affected by dietary protein and ovariectomy but increased with time, as well as kidney weight which shows the continuous development of kidney at this age of 15 month in rats. There were no difference in urinary hydroxyproline, serum ALP, and PTH among experimental groups. The weights of femur, scapular, 4th vertebra increased with time, showing the skeleton continues to grow at this age in rats. However, Ca contents, Ca/wt, Ca/ash were decreased with time and tended to be lower in high protein group especially in femur. In conclusion, prolonged feeding of high protein diet deteriorated Ca metabolism and induced bone loss as time after menopause is extended.