An unusual case of traumatic false aneurysm following a puncture wound in the hand of a hemophiliac, despite Factor VIII replacement, demonstrates the necessity for careful evaluation of such patients when there is profuse and continued bleeding. Following surgical repair of the false aneurysm and the ulnar proper digital nerve of the thumb 17 days postinjury the patient had an uncomplicated recovery. Partial arterial laceration, the underlying pathology of this lesion, may be demonstrated by arteriography or surgical exploration.