Venous thromboembolism is a common and life-threatening complication in patients with advanced cancer. Chemotherapy has been identified as a risk factor for venous thromboembolism in cancer patients. The annual incidence of venous thromboembolism in cancer patients receiving chemotherapy is estimated to be about 10%. This risk increases up to 15-20% depending on type and combination of anticancer drugs. Hormonal and supportive therapies are also associated with increased risk for thrombembolic complications. Emerging data support the hypothesis that the occurrence of venous thrombembolic events in cancer patients is associated with a poor prognosis. The benefit of antithrombotic prophylaxis for venous thrombembolism in cancer patients receiving chemotherapy remains to be established. A randomized, placebo controlled, double blind trial (the PROTECHT study) designed to evaluate the efficacy and safety of the low-molecular-weight heparin nadroparin in the prophylaxis of venous and arterial thrombembolic events during chemotherapy has been recently completed and the results are currently analysed.