Venous thromboembolism (VTE) is a known complication of cancer which impacts on patient mortality and quality of life. Despite the known deleterious effects of VTE, the benefits of thromboprophylaxis have not been fully established. Identification of patients at highest risk of VTE could lead to better targeting of thromboprophylaxis. Several risk factors have been identified as contributing to VTE such as site and stage of cancer, age, comorbidities, obesity, and acquired prothrombotic states. Anti-cancer agents as well as the use of growth factor support have also been implicated in VTE. Recent data have identified biomarkers such as blood counts, tissue factor and P-selectin. In this review, we briefly summarize the risk factors for VTE as well as candidate biomarkers for VTE in cancer patients. We also review a validated risk score that can identify cancer patients at high risk for VTE. Risk stratification of cancer patients will allow clinicians to identify those patients at highest risk for VTE, who may derive the most benefit from thromboprophylaxis.