Some HIV-infected adults develop a lipodystrophy that includes significant changes in body shape, with fat loss in the face, arms and legs, and fat gain in the trunk. This lipodystrophy is often accompanied by hypertriglyceridemia, hypercholesterolemia, and hyperinsulinemia. So far, almost all cases of lipodystrophy have occurred in patients treated with protease inhibitor-containing antiretroviral therapies. Whether this lipodystrophy is a result of the use of protease inhibitors or other therapies employed for HIV infection, or is one of the many manifestations of HIV infection, and is unmasked by the longevity achieved by those treated with protease inhibitors remains uncertain. It has been suggested, although not proven, that this condition may be an adverse effect of protease inhibitor treatment. It is also unknown whether HIV-infected children develop significant lipodystrophy when exposed to protease inhibitors. We propose to investigate whether initiation of protease inhibitor-containing antiretroviral regimens in children with HIV infection affects the prevalence of dyslipidemia, insulin resistance, and alterations of body fat distribution, and to study the pathophysiology of these changes. The incidence of such abnormalities will be compared to children with non-HIV-related chronic infections, to HIV-infected children who are treated with protease inhibitor sparing regimen, and to healthy controls.