Cancer is a major risk factor for the development of venous thromboembolism (VTE). Conventional anticoagulant therapy with a vitamin K antagonist is more problematic in cancer patients due to an increased risk of recurrent VTE, and an increased risk of anticoagulant-related bleeding. In recent years, there has been a shift toward treating cancer patients with VTE with extended duration dalteparin. Dalteparin, a low-molecular-weight heparin, has been shown to be more effective, and as safe as conventional anticoagulant therapy, in cancer patients with VTE. This paper will (a) review the relationship between cancer and VTE, and (b) provide an overview of the role of dalteparin in the management of VTE in patients with cancer.