The half-lives and regeneration rates of clotting factors II, VII, and X in the plasma of anticoagulant-resistant and susceptible rats were determined. There is little or no difference in the half-lives of factors II and X in anticoagulant-resistant rats compared to susceptible rats, but the half-life of factor VII is longer in anticoagulant-resistant rats. In anticoagulant-resistant rats critical clotting factors appear to be carboxylated in preference to factor II, whereas the opposite occurs in susceptible rats; this may contribute to an animal's resistance status.