Venous thromboembolism is a common problem in cancer patients. It complicates both the surgical management of those with cancer and has been associated with varying risk for the development of clinical thromboembolism in patients receiving chemotherapy. Unfractionated and low-molecular-weight heparin have been validated both in terms of their efficacy and safety, in the prevention of venous thromboembolic disease in cancer patients undergoing surgical intervention and for the primary treatment and secondary prevention of recurrent venous thromboembolism. Beyond their uses in the prevention and treatment of thrombosis, low-molecular-weight heparins have recently been shown to prolong survival in patients with solid tumour malignancy.