The metastatic potential of TF-expressing tumor cells is strongly dependent on circulating hemostatic system components. Mice with genetic deficits in prothrombin (fII^Low), platelet function (Gαq⁻), or fibrinogen (Fib⁻) were intravenously injected along with appropriate littermate controls with either 4 × 10⁵ TF^WT or TF^ΔTail cells and pulmonary foci enumerated 21 days later. The data shown represent the total number of surface pulmonary foci for each mouse injected. The horizontal bars represent median values. All P values were generated using the Mann Whitney U test.