In reviewing the literature, the authors noted an important variation in stated and observed transfusion practice patterns among pediatric critical care practitioners, and in published guidelines on RBC transfusion. They also noted a paucity of clinical evidence with respect to RBC transfusion to critically ill children. There has been only one large randomized trial in adults, and the authors do not believe that the results from this trial should be generalized to critically ill children because of the many differences in children and their adaptive responses, and differences in disease processes. More research about anemia and RBC transfusion to critically ill children must be performed. The TRIPICU study is testing the safety of giving more or less RBC transfusion to stable critically ill children. Other studies must be done on the epidemiology and determinants of RBC transfusion in PICUs, on prevention of transfusion, and on alternatives to RBC transfusion (eg, erythropoietin).