To determine which anatomic position and marking techniques are valid for postoperative electrodiagnostic testing, ten patients were studied during anterior transposition of the ulnar nerve. Variables included skin and ulnar nerve distances measured anterior and posterior to the medial humeral epicondyle, and ulnar nerve conduction velocities over these distances, with the elbow flexed and extended, and with the ulnar nerve in the pretransposition and posttransposition location. The results of the study confirm that ulnar nerve conduction velocity is recorded as faster with elbow flexion preoperatively and elbow extension postoperatively when the skin measurement used for the distance is kept constant. Postoperatively, the most valid measurement of ulnar nerve conduction velocity was a skin distance that was posterior to the medial humeral epicondyle with the elbow extended.