Peak bone mass (PBM), which is achieved by early adulthood, is a key determinant of the lifetime risk of osteoporosis. Because the foundation for skeletal health is established so early in life, osteoporosis prevention begins by optimizing gains in bone mineral throughout childhood and adolescence. Heritable factors account for an estimated 60-80% of the variability in PBM, with diet, physical activity and hormonal status serving as important modifiers of bone accrual. Recent pediatric studies have clarified the tempo and magnitude of gains in bone mineral and the modulating effects of diet, activity and sex steroids. The challenge lies in designing effective means to reverse trends of decreased calcium consumption, increased sodium intake and diminished physical activity among children and adolescents. Equally important is raising the awareness of health care providers to recognize children at risk for suboptimal acquisition of PBM.