HE INCIDENCE OF DEEP VEIN thrombosis (DVT) is 1 per 1000 person-years. 1 The10-yearrecurrence risk is 30%. 2 Deep vein thrombosis can lead to life-threatening pulmonary embolism. 3 Deep vein thrombosis is caused by acquired and genetic risk factors. Acquired risk factors include age, hospitalization, cancer, pregnancy, hormone therapy, and surgery. 2 Family and twin studies indicate that genetics ac-countsforabout60%oftheriskforDVT. 4,5 Deficiencies of natural anticoagulants antithrombin, protein C, and protein S are strong risk factors for DVT; however, the variantscausingthesedeficienciesarerare and explain only about 1% of all DVTs. 6 Two more common genetic variants, Factor V Leiden (FVL) and prothrombin G20210A, have been consistently found to be associated with DVT 7,8 but still only explain a fraction of the DVT events. 6 It has been suggested that 2 or more risk factors are needed for thrombosis. 6,9,10 The identification of additional common gene variants associated with DVT will improve the ability to predict risk for DVT and increase understanding of this disease. Therefore, we investigated whether any of 19 682 primarily missense single-nucleotide polymorphisms (SNPs) were associated with DVT in 3 large case-control studies. METHODS Study Populations and Data Collection The 3 studies (LETS, MEGA-1 and MEGA-2) in the present analysis are derived from 2 large population-based case-control studies: the Leiden Throm-bophilia Study (LETS) 11 and the Multiple Environmental and Genetic Assessment of Risk Factors for Venous Thrombosis (MEGA study). 12 These