Randomization of HIV-infected children to treatment arms will be performed by computer-generated random numbers (SAS version 8.2 for Windows, SAS Institute, Cary, NC). Randomization will stratify by sex and age (e.g., > or < 14 years) in order to ensure that treatment groups are balanced with respect to these variables. Block randomization will be used to ensure that the number of subjects in each arm remains approximately similar over time. A randomization sequence will be generated by the study biostatistician and communicated to the research pharmacist who will dispense active or placebo medication as subjects are enrolled.