The epidemiology of deep vein thrombosis in adolescents has 2 potential associations. First, there is a demonstrated association with a congenital anomaly of the inferior vena cava (Dean SM, Tytle TL. Vas Med. 2006;11:165-169; Schnieider JG, Eynatten MV, Dugi KA, et al. J Intern Med. 2002;252:276-280). Secondly, resistance to activated protein C as a result of factor V Leiden is associated with thromboembolic disease at an early age (Price DT, Ridker PM. Ann Intern Med. 1997;127:895-903). Imaging modalities, central venous catheters, and improved life expectancy for critically and chronically ill children have resulted in an increased diagnosis of thromboembolic disease in the pediatric population (Journeycake MM, Manco-Johnson MJ. Hematol Oncol Clin N Am. 2004;18;1315-1338), and evaluation for thrombophilia should be performed for any child with thromboembolic disease.