A 13-year-old girl with cold agglutinin syndrome caused by anti-i was serologically positive for Epstein-Barr virus. The anti-i had a high titer at 4°C and high thermal amplitude (reacting up to 37°C with both cord i RBCs and the patient's autologous RBCs). The patient's hemoglobin dropped to 48 g/L. The age of the patient, the severity of the hemolysis, and the antibody specificity were unusual features of cold agglutinin syndrome. Transfusions with adult (I) red blood cells were effective.