Thromboembolic disease affects about 15% of cancer patients and presents a challenge to the oncologist for both prophylaxis and treatment. Although long known to be associated with malignancy, the underlying biochemical mechanisms are poorly understood. Both low-dose warfarin and low molecular weight heparin are effective strategies for prophylaxis of venous thromboembolism, including those involving venous access devices. Current treatment options for venous thromboembolism include heparin (unfractionated and low molecular weight), warfarin, and internal vena cava filters. The appropriate use of these therapeutic options in cancer patients is reviewed herein. There is suggestive evidence that heparin may be superior to warfarin in the long-term treatment of venous thromboembolism. Whether anticoagulants might also improve cancer survival rates independent of their effect on thromboembolism deserves further investigation.