The vast majority of vascular anomalies of infancy and childhood can be biologically classified as hemangioma or vascular malformation. Hemangiomas are benign neoplasms that proliferate rapidly in infancy only to involute in early childhood. The majority of hemangiomas do not need treatment. Pharmacologic therapy, with corticosteroids or interferon-alpha-2a, is indicated for lesions that threaten vital function or are grossly deforming. Vascular malformations are not tumors, but rather vessel abnormalities due to errors of vascular morphogenesis. They derive from embryonal capillary, venous, arterial, or lymphatic channels, or combinations thereof. The appearance, clinical behavior, and therapy differ based on their channel types. All too often, unfortunately, children with vascular anomalies are shuffled from physician-to-physician because a single practitioner, even a specialist, does not have sufficient knowledge to properly treat the vascular lesion. The authors recommend that every major referral center have a multidisciplinary "Vascular Anomalies Team." We also endorse a biologic classification of vascular lesions to facilitate interspecialty communication regarding diagnosis, natural history, and therapy.