To assess the influence of puberty and its associated changes in body weight and height on bone mineral density (BMD), lumbar spine (L2-L4) and femoral neck BMD were measured in 74 healthy, active children (9-16 years) using dual-photon absorptiometry. Competitive swimmers were recruited to minimize the potential effect variability in mechanical loading regime may have on bone density of the lumbar spine. Tanner staging was used to assess stage of puberty. Current dietary calcium intake was assessed by analysis of 6-day dietary records. Significant differences in spinal and femoral neck BMD occurred between early (Tanner 1 and 2) and late stages of puberty (Tanner 4 and 5), P