BACKGROUND:: The objective of this study was to evaluate the cutaneous vascular territories of the circumflex scapular artery and the areas supplied by perforators from neighboring anatomical vascular territories, and also to define the safety limits of circumflex scapular artery-based flaps by means of fresh cadaver injection studies. METHODS:: A total of 15 dorsal thoraxes from eight fresh cadavers were used in this study. After saline irrigation, contrast medium was injected into the subclavian artery of each specimen. Each full-thickness specimen of the posterior hemithorax was then radiographed to characterize vascular networks. RESULTS:: The primary zone of the circumflex scapular artery was calculated to be 93.8 ± 16.1 cm, which occupies a region smaller than that of the scapula. However, by capturing the secondary zone, which was composed of the territories supplied by adjacent perforators of the thoracodorsal artery, the dorsal intercostal artery, and the transverse cervical artery, potential flap survival dimensions extended beyond the scapular region. In fact, the potential zone was increased to 307.7 7 ± 55.3 cm, which extended beyond the scapular spine, the inferior angle of the scapula, the posterior axillary line, and close to the midline of the back. CONCLUSIONS:: The circumflex scapular artery is an appropriate source for harvesting a large fascial and fasciocutaneous flap based on a single perforating vessel. Surgeons should understand the limits of the circumflex scapular artery-based flap to make best use of it.