The purpose of this study was to determine the effect of prior use of highly active antiretroviral therapy (HAART) on outcome of human immunodeficiency virus (HIV)- patients admitted to intensive care units (ICUs). This study was a retrospective chart review of 242 HIV-infected patients who required 259 consecutive admissions to a university-affiliated hospital ICU during a 3-year period. Patient demographics, CD4 count, admission diagnosis, prior HAART, Pneumocystis jiroveci prophylaxis, length of stay, and ICU and hospital mortality were determined. Overall hospital mortality was 39%. Comparing patients who had received HAART before an ICU admission to those who had not, we found no difference between ICU or hospital mortality, need of mechanical ventilation, ICU and hospital length of stay, and incidence of P jiroveci. Pulmonary diagnosis was the most frequent ICU admission diagnosis (30%). Logistic regression analysis showed HIV-related illness and mechanical ventilation were significant independent predictors of increased hospital mortality.