The increased risk of thrombosis-related morbidity and mortality in patients with cancer remains, even in the face of anticoagulant therapy. Moreover, recurrent venous thromboembolism (VTE) complicates the management of cancer and adversely affects quality of life and survival. Until recently, initial therapy with unfractionated heparin or low-molecular-weight heparin (LMWH) followed by long-term therapy with an oral anticoagulant was the standard of care for the secondary prevention of acute thromboembolism in most patients. However, according to the results of the CLOT trial (Randomized Comparison of Low-Molecular-Weight Heparin Versus Oral Anticoagulant Therapy for the Prevention of Recurrent VTE in Patients With Cancer), extended LMWH therapy with dalteparin represents an alternative to standard oral anticoagulation. In terms of efficacy, the incidence of recurrent VTE in patients receiving dalteparin was half that of those receiving warfarin (27 of 336 patients vs 53 of 336 patients, respectively), for a 52% relative risk reduction. The incidence of major bleeding in this trial was not significantly different in the two arms. Although this LMWH regimen is supported by the latest practice guidelines of the American College of Chest Physicians, the question of whether long-term treatment with LMWH in cancer patients actually affects survival apart from the benefits of thromboprophylaxis remains to be answered.