Inherited and acquired thrombophilia are well-known risk factors for venous thromboembolism. The incidence of thrombotic events in cancer patients is increased compared to normal population. Data on inherited thrombophilia and cancer is limited. Most studies are small, and results are varied by geography, tumor type, stage of disease and therapy. Nevertheless, it seems that factor V Leiden and prothrombin mutation may increase VTE risk in cancer patients. Data also exist for hyperhomocysteinemia. Cancer patients with thrombophilia who have a central vein catheter are a special group with increased venous thrombotic event (VTE) risk. Among acquired risk factors, antiphospholipid antibodies are common in cancer patients, especially in lymphoproliferative diseases. Published data suggests that the risk of thrombotic events, venous and arterial, is increased in cancer patients with antiphospholipid antibodies. The questions of screening cancer patients for inherited thrombophilia or antiphospholipid antibodies are unclear. There is no data on primary VTE prophylaxis in cancer patients with thrombophilia and prophylaxis for cancer patients with central vein catheters is controversial. Copyright 2009 S. Karger AG, Basel.