Peak adult bone mass is determined in each individual by a combination of endogenous and environmental factors. Insufficient accumulation of skeletal mass by the time young adulthood is reached appears to enhance the likelihood of fractures later in life. It is speculated that environment (nutrition and exercise) contributes to about 20% of the variance in bone mass. Although much is yet to be learned about how diet contributes to skeletal growth and development, it now appears that calcium intake may be an important factor in the attainment of peak bone mass. A review of the scientific literature suggests that the current recommended dietary allowance (RDA) for calcium may not be high enough to optimize the genetically programmed peak bone mass in a substantial number of growing individuals. New standards for dietary calcium intakes during growth may be indicated.