The vascular noninvasive studies of 289 consecutive cardiac surgery patients were reviewed to better understand hand blood-flow physiology in an older population with vascular disease. The radial artery was found to be more important to pulsatile digital blood flow than the ulnar artery. In more than 20 percent of hands, the thumb and the index and fifth fingers lost pulsatile blood flow with radial artery compression at the wrist compared with only 5 percent with ulnar artery compression. The maintenance of pulsatile digital blood flow did not follow anatomic patterns of blood vessels previously presumed to be of paramount importance. The hand acts more like a single vascular bed than it does like two separate systems with a connecting arch.