A new skin or fascial flap is described, based on the dorsal ulnar artery. In hundred fresh cadaveric forearms this vessel was constant with a diameter of 1 to 1.3 mm, passing dorsally from the ulnar artery deep to the flexor carpi ulnaris muscle. It supplies the skin and the fascia in the distal two thirds of the ulnar side of the forearm (length from 9 to 20 cm; width 1.5 to 10 cm). A flap based on this vessel can cover defects of the dorsal and palmar aspects of the hand and wrist, the thenar and the hypothenar eminence. It can be used as a fascial flap to avoid fibrosis around the median nerve and the tendons. The authors show the anatomy and some clinical cases.