In recent years, a growing body of evidence has provided the convincing demonstration of a strong association between cancer and venous thromboembolism. This relationship is further supported by the risk of developing overt malignancy in patients with idiopathic venous thromboembolism. However, the cost-to-benefit ratio of an extensive diagnostic work-up aimed at identifying an occult cancer in patients with spontaneous thromboembolism still has to be demonstrated. During prolonged immobilization from any cause, and following surgical interventions, patients with cancer are at a remarkably higher risk of venous thromboembolism than patients free from malignant disorders. Standard heparin in adjusted doses or a low-molecular-weight heparin in doses commonly recommended for high risk surgical patients represent the prophylactic treatment of choice for cancer patients undergoing an extensive abdominal or pelvic intervention. Furthermore, the risk of thrombotic episodes is increased in cancer patients by chemotherapy and by the use of indwelling central venous catheters. Recent data suggest a positive benefit-to-risk ratio with the systematical use of fixed mini-dose of warfarin in both conditions. After experiencing an episode of thrombosis, cancer patients remain at risk of recurrence for as long as the cancer is active. Therefore, they should be protected by a long-term course of oral anticoagulation. The risk of recurrent thrombotic events despite adequate anticoagulation is higher in patients with cancer than in those without cancer. The routine use of long-term subcutaneous heparin therapy rather than oral anticoagulants should be reserved for patients in whom warfarin has been ineffective. Can antithrombotic drugs improve survival in cancer patients? In cancer patients affected by deep-vein thrombosis, the treatment with low-molecular-weight heparins has been reported to lower mortality at a higher extent than the standard heparin therapy. Such an observation suggests that these agents might develop an antineoplastic activity.