Lack of TFPI does not affect the dynamics of clot formation in Par4^−/− mice. Thrombus formation in the femoral vein was induced by electrolytic injury. For each genotype, 2 thrombi were formed in each of 3 mice, 1 in each femoral vein, totaling 6 thrombi analyzed. Lines represent the mean and error bars the standard deviation of the relative intensities for accumulation of rhodamine 6G-labeled platelets and AlexaFluor-647–labeled anti-fibrin. Platelet accumulation is significantly decreased in both Par4^−/− (P < .01) and Tfpi^−/−:Par4^−/− (P < .001) mice compared with wild-type mice. It is not significantly different between Par4^−/− and Tfpi^−/−:Par4^−/− mice (P > .05). Fibrin formation is not different among the genotypes (P > .05 for all comparisons).