Background: The posterior intercostal arteries form the largest angiosome in the torso by means of their many perforators to the skin, the arteries of which are proposed to be the vascular pedicle of an island flap. Using these perforators, the authors developed a new flap, the dorsal intercostal artery perforator flap, harvested in the back. Methods: An anatomical study was conducted on five fresh human cadavers injected with a lead oxide-gelatin mixture as a radiopaque agent. The study consisted of the cadaver dissection and the angiographic studies to map the dorsal intercostal artery perforators in detail. Results: Each of the fourth to twelfth posterior intercostal arteries consistently supplied the dorsal perforators. Those derived from the fourth, fifth, sixth, tenth, and eleventh posterior intercostal arteries were the dominant direct cutaneous perforators. They were located within 5 cm of the spinous processes of the vertebrae and were clinically detectable by Doppler probe preoperatively. Eleven dorsal intercostal artery perforator flaps were applied in 10 cases. In nine cases, the muscles of the latissimus dorsi, the trapezius, or the scapular circumflex artery had been sacrificed in previous operations. The maximum flap dimension was 31 x 13 cm. All flaps showed stable postoperative blood circulation and survived completely, except for marginal necrosis in the largest flap. No functional loss attributable to flap harvest was recognized. Conclusion: Flap extendibility and less invasiveness without sacrifice of the underlying muscles have proved that the dorsal intercostal artery perforator flap is a new reconstructive option in the back, where suitable flaps are often proposed.