Objective: Although highly active antiretroviral therapy (HAART) resolves a significant proportion of anemia among HIV-patients in Western cohorts, outcomes may vary in developing countries, due to a higher prevalence of nutritional deficiencies, intestinal parasites, tuberculosis, and opportunistic infections. The purpose of this study is to describe the prevalence of, factors associated with, and influence of HAART on, anemia among HIV-infected individuals in South India. Methods: To examine factors associated with anemia, the first-recorded hemoglobin values for adults who visited an HIV tertiary care center in Chennai, India between January 1996 and April 2006 were collected (n=7069). Univariate and multivariate regression analyses were performed to examine associations between anemia and stage of HIV disease, co-morbidities, and medications. To examine the influence of HAART use on anemia on a smaller subset of patients (n=401), the mean of baseline hemoglobin values measured within 3 months prior to HAART initiation was compared to the mean of follow-up hemoglobin values collected between 3-12 months after HAART initiation. A similar analysis based on the time of AIDS onset was performed for a control group of patients with clinical/immunological AIDS who never received HAART (n=77). Results: The prevalence of anemia in the overall cohort was 40% by the WHO definition. While 22% of patients with CD4 counts >500 cells/ÃL had anemia, this increased to 60% for those with CD4 counts