The immune reconstitution inflammatory syndrome (IRIS) associated with highly active antiretroviral therapy (HAART) was studied in rural Ethiopian HIV-infected patients. Review of 1002 charts in an outpatient clinic was conducted. The median CD4 count was 89 cells/mm3. Ninety-eight patients were hospitalized after initiation of HAART, of whom 74 were hospitalized for manifestations of IRIS (ie, 7% of patients on HAART). Of the 74 patients hospitalized with IRIS, 27 patients had tuberculosis; 12 patients, cryptococcal meningitis; 7 patients, toxoplasmosis; 6 patients, pneumonia and/or effusion; and 5 patients, Pneumocystis jiroveci pneumonia (PCP). Ten adult patients were admitted with gastroenteritis, heretofore not recognized as a manifestation of IRIS. Eighty-one percent of IRIS patients were hospitalized within 3 months of beginning HAART and 99% by 6 months. Of those hospitalized with IRIS, 4 patients (5%) died while in the hospital (3 with cryptococcal meningitis). Thirty-seven or 50% of those hospitalized with IRIS were lost to medical follow up, thus the mortality rate is likely a gross underestimate of the severity of IRIS. In resource-poor settings where the primary goal is to initiate HAART, IRIS may go unrecognized and have fatal consequences.