Prognostic factors were evaluated in 25 children with autoimmune hemolytic anemia (AIHA). Patients with acute disease were generally 2-12 years of age at diagnosis, had a sudden onset of symptoms, showed low reticulocyte counts, had decreased numbers of nucleated red blood cells or early white blood cells precursors on peripheral blood smear, and had normal platelet counts. They responded well to steroids and the disease resolved within 6 months without mortality. Children with chronic AIHA were generally less than 2 or greater than 12 years of age, had a more prolonged onset of symptoms, had increased reticulocyte counts, had increased numbers of nucleated red blood cells and early white blood cell precursors on peripheral blood smear, and had decreased platelet counts. They had a variable response to steroids frequently requiring other modalities of treatments and had a mortality of 25%. Females in this group had a significant incidence of associated diseases. Autoantibodies were characterized as to temperature sensitivity and reaction with class specific antiglobulin reagents and were related to the type of AIHA.