BACKGROUND:: The authors have used pectoral intercostal perforator flaps to reconstruct burned or injured hands by staged transfer. This flap is designed with a narrow skin pedicle that includes intercostal perforators from the fifth to eighth intercostal spaces, with a wide flap area that lies on the upper abdomen. The distal area is thinned down to the subdermal vascular network level
 thus, such flaps are called "superthin flaps" or subdermal vascular network flaps. In this article, the authors discuss the arterial networks associated with this flap and present clinical cases. METHODS:: The authors performed an anatomical study using 13 cadavers to obtain angiograms and dissect the anterior chest and abdominal region. Clinically, the authors retrospectively analyzed 21 cases over 13 years. RESULTS:: Anatomically, the anterior intercostal regions could be divided into three segments with regard to vascular supply to the skin and subcutaneous layer. In particular, in the fifth to eighth intercostal spaces, perforators communicated with one another to form a "latticework" pattern. In addition, the vascular territories participating in the pectoral intercostal perforator flap, that is, the intercostal perforators, the superior epigastric artery system, and the deep inferior epigastric artery system, linked with each other through choke vessels. In the authors' clinical cases, functional and aesthetic results were satisfactory. CONCLUSIONS:: The pectoral intercostal perforator flap was supported by the arterial networks among perforators in the intercostal spaces and in the upper abdomen. This flap is one useful method for reconstruction of the hand region, providing good quality in terms of thinness and texture. © 2009 by the American Society of Plastic Surgeons.