Optimizing peak bone mass in early life may reduce osteoporosis risk in later life. Such optimization may be partly dependent upon diet. In the present study, nutrient intakes and selected lifestyle parameters were assessed in adolescent Subjects (238 males. 205 females, aged 15 y) and again, in the same subjects. on one occasion in young adulthood (aged between 20 and 25 y). The extent of the relationships between these parameters and bone mineral density (BMD). dual energy X-ray absorptiometry (DXA). lumbar spine (L2-L4). and femoral neck measured concurrently with diet in young adulthood only. was assessed. Adjusted linear regression models were constructed. Variables included a Measure Of pubertal status (at age 15 y). age (at young adulthood), height, weight. physical activity, smoking, and mean daily intakes of energy, calcium. protein. vitamin D. phosphorus, total fat. and alcohol. In both sexes, bode weight at adolescence and young adulthood as the only factor consistently positively associated with BMD at both measurement sites. Effects of nutrient intake on BMD were inconsistent. Vitamin D and Calcium intakes reported by female adolescents showed significant positive relationships with BMD measured in young adulthood (vitamin D Measured at the lumbar spine: calcium Measured at the femoral neck). The positive relationship between vitamin D and BMD remained significant at young adulthood. but at the femoral neck rather than Ut the lumbar spine. Also in females, intakes of phosphorus and the calcium:phosphorus ratio (Ca:P) at adolescence were strongly negatively related to femoral neck BNID measured at young adulthood. In males, however, Ca:P reported at young adulthood had a significant positive relationship with lumbar spine BMD, whereas Ca:protein was negatively associated with BMD at the lumbar spine. Intakes of Ca reported by adolescent males also had a strong negative effect on lumbar spine BMD measured at young adulthood.