 ARV failure at the PIDC is generally assessed on clinical grounds weight loss, diarrhea, fever, opportunistic infection OI etc. The PIDC has a fairly sophisticated data management system. In those children having clinical failure to the ARVs after initial therapy, blood for HIV-1 viral load, subtype and genotype will be drawn. This blood will be frozen and shipped to the University of Wisconsin for analysis. On site Dr. Kekitiinwa clinical data will be collected. This data will include age, sex, physical findings and clinical course on ARVs. More specifically, the reason for ARV failure was: the occurrence of OI, wasting, recurrence of diarrhea, other symptoms of HIV, or toxicity to the ARV tolerability. All blood samples will be labeled only with a number that corresponds to the identity of the patient. This number will be kept by Dr. Graziano. These samples will then be Federal Expressed on dry ice to the University of Wisconsin where they will be evaluated for HIV-1 subtype and genotype. 