 The overall design of this study is to prospectively collect cohort clinical and virologic data from children ages birth to 16 years started on ARV therapy during a 12 month period of enrollment about 110 children who qualify for PEPFAR ARV treatment. The only inclusion criteria is the child receives ARV therapy. The only exclusion is refusal on the part of the patient or family to have blood drawn and records examined. Children receiving ARV therapy in this time period will be approached and recruited for this study by the attending physician. This study is approved by the University of Wisconsin Hospital and Clinics and Mulago Hospital IRBs. 