A 3-year-old boy presented with the fever, conjunctivitis, rash, and lymphadenopathy diagnostic of Kawasaki disease. Treatment with antibiotics, aspirin, and intravenous immunoglobulin was instituted. The hematocrit decreased from 35 percent on admission to 11 percent by hospital Day 10, and the white cell count had increased from 13.7 to 42 x 10(3) per microL, and the patient had a leukoerythroblastic blood smear. The direct antiglobulin test demonstrated IgG but not complement on the red cell (RBC) surface. An acid eluate reacted (titer of 4) with all panel cells in the antiglobulin phase. Intravenous immunoglobulin from the same lot used for treatment did not contain antibody that reacted with the patient's group O RBCs or a panel of group O RBCs, but did contain IgG anti-A and -B (titer of 4). The patient received a transfusion and was given methylprednisone. The direct antiglobulin test and acid eluate were negative 4 days later. The patient had an uneventful recovery. The distinction between antibody-mediated hemolytic anemia and autoimmune hemolytic anemia is important in the treatment of this disease.