Complex factors, including substances in cancer cells, cancer treatment effects, and venous stasis associated with chronic illness, blood vessel wall injury, and immobility, interact to place patients with cancer at risk for thrombosis. This article describes the etiology, clinical manifestations, diagnostic tests, and treatments for venous and pulmonary emboli associated with cancer. It explores the nurse's role in assessing patients who are at risk, managing symptomatic thrombosis and primary and secondary prevention of emboli, and administering anticoagulant therapy. As growing numbers of patients are treated in outpatient settings, oncology nurses play a critical role in the coordination of care for patients at risk for thrombosis. A nursing care plan summarizes key nursing strategies for assessment and intervention.