Standard dietary calcium requirements for various age groups have mostly been estimated and derived from studies performed in Caucasian populations. This is the first calcium absorption study performed in Chinese children who may not drink milk regularly. A technique using double-labelled stable calcium isotope was employed to measure true fractional calcium absorption. Thirty four 7-year-old children with calcium intakes ranging from 172 to 1641 mg/d were studied. They were then randomised into two groups, one being given 300 mg elemental calcium daily for six months, the other being given placebo tablets daily for the same period. It was found that the mean true fractional calcium absorption was 63% and 55% in children whose daily calcium intake was below 500 mg and above 500 mg respectively. Both absorption rates were much higher than those reported in Caucasian children, and there was a physiological increase from 58% to 64% in true fractional calcium absorption as children grew from age seven to seven and a half. Calcium supplementation caused a significant fall in calcium absorption (61% to 56%). The change in calcium absorption during the six months of supplementation was significantly different to the control values, even after adjusting for other baseline variables. It was concluded that calcium absorption is affected by calcium intake and calculations of recommended daily calcium intakes should take this into account.