The purpose of this study was to compare the use of lamivudine (3TC) or emtricitabine (FTC) alone vs. continuing a failing highly active antiretroviral therapy (HAART) regimen in HIV infected children, adolescents and young adults. The study was to see if there were changes in the HIV virus and if there were differences in immune function, viral load and medication side effects between the two groups over 28 weeks. Participants were assigned to either take 3TC or FTC alone or continue on his/her current failing HAART regimen. During the first 28 weeks of this study, if the participant was randomized to the continue HAART arm, he/she was not switched to a different or new, potentially suppressive HAART regimen, but continued on the current failing HAART regimen. However, if continuing HAART, the participant might be switched to a new regimen if their provider felt that it was clinically needed or the participant met certain study endpoints (e.g., drop in CD4, increase in viral load).