1. The forearm and hand circulation in nine patients with a surgically created side-to-side fistula between the radial artery and a nearby superficial vein in the lower forearm has been investigated.
2. Dilated veins on the dorsum of the hand communicated with the fistula without intervening valvular obstruction. Skin temperature of both forearm and hand was greater on the side with the fistula in all cases.
3. Inflation of an occlusion cuff distal to the fistula markedly reduced apparent fistular flow.
4. It is concluded that the fistulae result in increased blood flow to the hand by retrograde flow from the fistula into the hand veins. Hand as well as forearm must be included in the plethysmographic measurement of blood flow in such cases.