The purpose of this research was to investigate the effects of caffeine and calcium levels on calcium utilization in female rats of different ages. Calcium utilization was compared in female rats of different age( 4 weeks and 12 months) fed various levels of caffeine(0 and 7 mg/100g body weight) and calcium (50, 100 and 200% of requirement) for 3 weeks. Feed intake of the caffeine groups were lower than that of the no-caffeine groups. body weight gain was lowest in the high-caffeine and low-calcium group. Serum calcium levels of young rats were higher than those of adult rats. There were no significant differences in tibial calcium content among the caffeine and calcium -groups. Fecal calcium excretion increased as the level of dietary calcium was increased. Urinary calcium excretion increased as the levels of caffeine and dietary calcium were increased. With increasing levels of dietary calcium , daily calcium retention was accelerated, but apparent calcium absorbability was diminished. The results of this study suggest that caffeine consumption promotes urinary calcium excretion. However, increase in dietary calcium resulted in higher calcium retention . These findings indicate that high caffeine consumption may increase dietary calcium requirements. Therefore, it could be suggested that the supplementation of dietary calcium may counteract the negative effect of caffeine intake on calcium utilization.