Survival of low-TF mice with different levels of FXI. Low-TF;FXI^+/+, low-TF;FXI^+/−, and low-TF;FXI^−/− mice were assessed in a 6-month survival study. As expected, 27% (3 of 11) of low-TF;FXI^+/+ mice died by 6 months with evidence of pulmonary hemorrhage. By comparison 10% (2 of 21) of low-TF;FXI^+/− and 25% (3 of 12) of low-TF;FXI^−/− mice died by 6 months with evidence of pulmonary hemorrhage. No significant difference in survival was observed between groups. P > .05, log-rank test.