The transition of childhood to adulthood includes many changes to nearly all parts of the body and that is certainly true of blood and the coagulation system. Some disorders, like iron deficiency anemia, develop as the result of rapid growth. Approximately 10% of American adolescents are anemic and the prevalence is far greater in high-risk populations, such as urban, indigent African-American adolescents, in which 40-50% of young women are anemic. Adolescents at greater-than-average risk for developing iron deficiency anemia, such as athletes involved in lengthy, intense physical activities and pregnant adolescents, should be screened for anemia. Other blood problems are inherited but the first manifestations may not emerge until adolescence, as in the case of an adolescent girl discovered to have von Willebrand's disease during the evaluation of excessive menstrual bleeding. Besides iron deficiency anemia and von Willebrand's disease, this review focuses on management of other common hematologic disorders seen in adolescent patients, including immune thrombocytopenic purpura, hemophilia, thrombocytosis, and hypercoagulable disorders.