Hematologic malignancies account for almost 40% of all cancers in children. Hemorrhage is the most common cause of early death in children with leukemia. Furthermore, major bleeding episodes lead to shorter survival and increased resource use. Potential risk factors for bleeding include hyperleukocytosis, immunophenotype of leukemia (especially acute promyelocytic leukemia), thrombocytopenia, and associated infections. Successful management of a bleeding episode is dependent on prompt identification of a child at high risk for bleeding, and should be directed at the replacement of blood products as well as to the aggressive therapy for underlying risk factors. Although in recent years there is a favorable decline in the hemorrhage-related mortality, the overall prevalence and the extent of morbidity posed by this potentially fatal complication, including disease outcome in children with hematologic malignancy, is largely unknown. In addition, there are no evidence-based guidelines for prophylactic blood or blood product transfusions. Prospective studies are required to define the epidemiology and risk factors predisposing children with hematologic malignancy to bleeding and to develop management guidelines.