The use of protease inhibitors is increasing in HIV-infected children because this treatment has resulted in improved body weight, improved immune status and less hospitalizations. However, recent reports suggest that these drugs may also be associated with some negative side-effects, specifically a syndrome of diabetes and fat redistribution. Development of the fat redistribution/diabetes syndrome has recently been reported in HIV-infected children, as well as in adults. Diabetes is associated with complications such as increased heart disease, eye disease and loss of kidney function. Thus development of diabetes is a significant problem which could outweigh the benefits obtained by treating patients with protease inhibitors. One major cause of diabetes is lack of normal response to insulin (insulin resistance). Insulin resistance tends to be worse in family members where one or more parent has diabetes, and is also worse in certain ethnic groups. The first major purpose of our study is measure insulin resistance in HIV-infected children who do not take protease inhibitors, and compare our findings to those from patients who are treated with protease inhibitors. We will also follow patients newly treated with protease inhibitors for two years to evaluate changes in insulin sensitivity. These results will be correlated with each patient's family history of diabetes and with ethnicity, and should help us better predict which children are "at risk" for development of diabetes from protease inhibitor therapy. Children with HIV infection often have problems with gaining enough weight and with poor linear growth (height). One likely reason for this is the way their bodies use and store protein. The second purpose of our study is measure protein turnover and to correlate our findings with growth data. We also plan to study the effects of protease inhibitor therapy on protein turnover. We believe that these studies will provide knowledge to help clinicians formulate recommendations for nutritional and medical therapy.