We read with interest Gartrell's recent report of a woman who developed a factor V inhibitor. Gartrell noted in his report that the inhibitor appeared to exhibit time dependence, as the mixing study showed slightly more prolongation of both the PT and the aPTT after 1 hr than immediately following mixing. We believe Gartrell's article may shed light on a recent intriguing case of a patient with factor V inhibitor at our institution.