One week after treatment with intravenously administered immune globulin and aspirin, a child with Kawasaki disease had persistent fever and an increase in coronary artery diameter to greater than 3 mm. Two additional doses of immune globulin were given intravenously. Rapid hemolysis occurred, followed by disseminated intravascular coagulation and serum sickness. Clinicians should be aware that immune globulin preparations contain antibodies to blood-type antigens that may cause significant hemolysis and disseminated intravascular coagulation.