It will include 225 HIV-infected patients from ACTG 152, as well as an additional 450 non-infected participants recruited for two comparison groups, one consisting of seronegative infants and children with perinatal exposure to HIV and a second group without perinatal exposure to HIV. AS PER AMENDMENT 10/24/96: Patients in the HIV-unexposed and uninfected group are discontinued from the study and remaining patients are reassigned to two new age groups: 3 months to 41 months and 30 days or 42 months to 9 years, 11 months, 30 days. Patients 33 months or older but less than 42 months are discontinued from the study, those patients less than 33 months at the time of enrollment are graduated from the study at the age of 42 months.