We hypothesize that indices of mineral metabolism are abnormal (low serum 25(OH)D and elevated PTH) and biochemical markers of bone formation and resorption are increased in HIV-infected children on HAART compared to normal controls and that indices of mineral metabolism and markers of bone formation and resorption will return toward normal in HIV-infected children and adolescents who are randomized to receive vitamin D and calcium supplementation. We will test this hypothesis first by comparing markers of bone turnover (osteocalcin, BALP and N-Tx) in HIV-infected and healthy children and adolescents enrolled in the cross-sectional study using independent samples t-test to compare means.