Highly active antiretroviral therapy (HAART) has dramatically reduced morbidity and mortality from HIV disease, but these benefits have not been conferred equally among all patient populations. Injection drug users (IDUs) have shown particularly less favorable outcomes, with HIV progression remaining at high levels, and IDU remains a significant risk behavior for the spread of HIV worldwide, with explosive epidemics in Eastern Europe, Russia, and Southeast Asia. It is therefore essential to develop and test strategies of HIV treatment that optimize outcomes for this population, in order to reduce morbidity and mortality and to curb secondary transmission.