Over the past five decades, the survival rate for children diagnosed with oncologic disease has dramatically increased from less than 20% to almost 80%. Accordingly, an area of growing interest and concern is the long-term effects of the patients' disease and therapy. Thromboembolic events (TEE) occur with greater frequency in children and adults with cancer and have been extensively studied in the latter population. However, given the relative infrequency of TEE in the general pediatric population and paucity of coordinated efforts, information on the incidence, nature and impact of thrombosis in children with cancer has been lacking until recently. In this chapter, we address the salient features of TEEs in the pediatric cancer patient.