Thrombin activatable fibrinolysis inhibitor (TAFI) is an important inhibitor of fibrinolysis. High TAFI antigen levels are associated with an increased risk of deep venous thrombosis (DVT). Because TAFI levels are partly determined genetically, we assessed the association between three TAFI gene polymorphisms (-438 G/A, 505 A/G and 1040 C/T), TAFI antigen levels and clot lysis times and the risk of DVT. Carriers of the 505G allele, which is associated with lower TAFI antigen levels than the 505A allele, showed an increased risk of DVT. This indicates that the relationship between TAFI and venous thrombosis is more complex than previously suggested.