High calcium intake during childhood has been suggested to increase bone mass accrual, potentially resulting in a greater peak bone mass. Whether the effects of calcium supplementation on bone mass accrual vary from one skeletal region to another, and to what extent the level of spontaneous calcium intake may affect the magnitude of the response has, however, not yet been clearly established. In a double-blind, placebo-controlled study, 149 healthy prepubertal girls aged 7.9+/-0.1 yr (mean+/-SEM) were either allocated two food products containing 850 mg of calcium (Ca-suppl.) or not (placebo) on a daily basis for 1 yr. Areal bone mineral density (BMD), bone mineral content (BMC), and bone size were determined at six sites by dual-energy x-ray absorptiometry. The difference in BMD gain between calcium-supplemented (Ca-suppl.) and placebo was greater at radial (metaphysis and diaphysis) and femoral (neck, trochanter, and diaphyses) sites (7-12 mg/cm2 per yr) than in the lumbar spine (2 mg/cm2 per yr). The difference in BMD gains between Ca-suppl. and placebo was greatest in girls with a spontaneous calcium intake below the median of 880 mg/d. The increase in mean BMD of the 6 sites in the low-calcium consumers was accompanied by increased gains in mean BMC, bone size, and statural height. These results suggest a possible positive effect of calcium supplementation on skeletal growth at that age. In conclusion, calcium-enriched foods significantly increased bone mass accrual in prepubertal girls, with a preferential effect in the appendicular skeleton, and greater benefit at lower spontaneous calcium intake.