The degree of positive calcium balance in young individuals necessary to achieve peak bone mass and density is unknown. To assess calcium requirements and metabolism during acquisition of peak bone mass, 487 calcium balance studies from published reports were analyzed. The results suggest that 1) calcium intake and skeletal modeling and turnover determine calcium balance during growth, 2) the highest requirements for calcium are during infancy and adolescence and then during childhood and young adulthood, 3) to meet high calcium requirements, infants and adolescents have higher calcium absorption, 4) calcium absorption during rapid bone modeling and turnover is mediated by the Nicolaysen's endogenous factor, 5) urinary calcium reaches its maximum by the end of puberty, 6) calcium intake has little influence on urinary calcium excretion during the period of rapid growth, 7) the recommended dietary allowance for calcium should be higher than the amount currently established for children, adolescents, and young adults to ensure a level of skeletal retention of calcium for maximal peak bone mass, and 8) clinical trials with increased calcium intakes in each age segment of young populations are needed to clarify the above trends.