Objective: Identify the incidence, the common causes of The Immune Reconstitution Inflammatory Syndrome (IRIS). Identify the rate of patients with severe adverse effects ARV be admitted. Subjects: 252 patients who started antiretroviral (ARV) therapy within 3 years from 2010 to 2012 at National Hospital of Pediatrics. Methods: Retrospective descriptive study. Results: Of 252 patients surveyed, there are 10 percent of the patients experienced IRIS, 5.5 percent having the side effects of ARVs. Of 25 patients with IRIS, pneumonia accounts for 44 percent, upper respiratory tract infection 24 percent, tuberculosis 20 percent, viral fever 8 percent, CMV retinitis 4 percent. Of 14 patients with manifestations of ARV side effects, allergy accounts for 57 percent, anemia 21.5 percent and acute diarrhea 21.5 percent.