A 66-year-old man with homozygous deficiency of factor VII (less activity than 4 percent of normal) had a minimal hemorrhagic tendency and severe coronary atherosclerosis, and underwent aortocoronary saphenous vein bypass surgery. Although plasma factor VII coagulant activity and cross-reacting material were markedly reduced, comparable amounts of factor VII antigen were detected in peripheral blood mononuclear cells of both the patient and of a normal subject by Western blotting techniques. Accelerated coagulation was observed following brief exposure of the patient's phytohemagglutinin-stimulated peripheral blood mononuclear cells to low concentrations of ambient factor VII in vitro. Evidence indicates that factor VII plays a role in vivo in both hemostasis and atherogenesis and it might be assumed that factor VII deficiency would both predispose to excessive bleeding and forestall atherosclerosis. However, these observations suggest that factor VII-mediated thrombin generation may proceed by partitioning of small amounts of factor VII on tissue factor-expressing cells and that factor VII contained within monocytes may facilitate tissue factor-induced coagulation by these cells. These features may provide efficient coagulation activation despite a deficiency of the plasma coagulant protein. The current results may explain, at least in part, the minimal bleeding tendency, and also the occurrence of thrombosis and atherosclerosis in certain persons with factor VII deficiency.