The role of reconstructive arterial surgery in the treatment of arteriovenous fistulas is now well established. However, as indicated by Hughes and Jahnke,1 it is often difficult to evaluate residual complaints after treatment without objective methods of study. We have recently applied the mercury strain gauge plethysmograph to the study of patients with peripheral arteriosclerotic vascular disease and found it to be most satisfactory.2 The mercury gauge is a very sensitive indicator of changes in the digital volume and permits measurement of systolic blood pressure at any level of the extremity. Employing this information, it is possible to localize the site and extent of arterial involvement, evaluate the distal arterial tree, and accurately determine the results of angioplastic surgery.3 This technique has been applied to the preoperative, operative, and postoperative study of 3 patients with acquired arteriovenous fistulas. The utility and value of this method is evident