© 2018 World Health Organization. Background. Severely immunocompromised human immunodefciency virus (HIV)-infected individuals have high mortality shortly afer starting antiretroviral therapy (ART). We investigated predictors of early mortality and "late presenter" phenotypes. Methods. Te Reduction of EArly MortaLITY (REALITY) trial enrolled ART-naive adults and children =5 years of age with CD4 counts < 100 cells/μL initiating ART in Uganda, Zimbabwe, Malawi, and Kenya. Baseline predictors of mortality through 48 weeks were identifed using Cox regression with backwards elimination (exit P > .1). Results. Among 1711 included participants, 203 (12%) died. Mortality was independently higher with older age; lower CD4 count, albumin, hemoglobin, and grip strength; presence of World Health Organization stage 3/4 weight loss, fever, or vomiting; and problems with mobility or self-care at baseline (all P < .04). Receiving enhanced antimicrobial prophylaxis independently reduced mortality (P =.02). Of fve late-presenter phenotypes, Group 1 (n = 355) had highest mortality (25%; median CD4 count, 28 cells/μL), with high symptom burden, weight loss, poor mobility, and low albumin and hemoglobin. Group 2 (n = 394; 11% mortality; 43 cells/μL) also had weight loss, with high white cell, platelet, and neutrophil counts suggesting underlying inflammation/infection. Group 3 (n = 218; 10% mortality) had low CD4 counts (27 cells/μL), but low symptom burden and maintained fat mass. Te remaining groups had 4%-6% mortality. Conclusions. Clinical and laboratory features identifed groups with highest mortality following ART initiation. A screening tool could identify patients with low CD4 counts for prioritizing same-day ART initiation, enhanced prophylaxis, and intensive follow-up.