Virologic response to highly active antiretroviral therapy (HAART) treatment of HIV infection depends on viral sensitivity to antiretrovirals and excellent medication adherence. Adolescents with vertically acquired HIV may require complicated regimens because of significant treatment experience and often have poor medication adherence. A retrospective chart review identified five adolescents with vertically acquired HIV and plasma HIV viral load rebound or nonresponse on a stable HAART regimen followed by a period of directly observed therapy (DOT) in a clinic or hospital setting with serial viral load measurements. Four subjects had a virologic response (mean decline, 1.15 log10) after DOT. A response to HAART can be seen despite antiretrovirals resistance using DOT and treatment-experienced patients seemingly unresponsive to HAART may be nonadherent even with reassuring adherence measures. A period of clinic-monitored DOT may allow diagnosis of nonadherence, discussion of medication barriers, and avoidance of unnecessary medication changes.