The aim of the present study was to assess the changes in flow patterns of forearm arteries produced by excision of the radial artery when harvesting the radial forearm flap. A prospective study using color duplex imaging for quantitative flow measurements was accomplished in 11 patients. After raising the radial flap, the forearm flow tended to increase overall, the ulnar (P = 0.04), the posterior interosseous (P = 0.003), and the anterior interosseous (P = 0.003) arteries being responsible for this tendency. Therefore, harvesting of a radial flap must not be considered as causing vascular morbidity in terms of blood supply to the hand.