This study is aimed to clarify the emerging point and course of the lateral branch of the fourth intercostal nerve and its supplying territory of the nipple-areolar complex. The branch nerves were dissected in the 16 breasts of 8 Korean cadavers through transaxillary and midsternal approach. An Agris-Dingmam dissector was useful for dissection and retraction. The emerging points of the lateral cutaneous branch of the fourth intercostal nerve through the intercostal spaces were within the bound of an ellipse with the major axis 26 mm and minor 10 mm. The center of the ellipse was located laterally 33 mm from a conjugate point of the lateral boarder of pectoralis major muscle and the fifth rib, and superiorly 8 mm from the upper margin of the fifth rib. Knowledge of the exact site of the emerging nerve branch is conducive to avoiding nerve injury during submammary or transaxillary subpectoral dissection for augmentation mammoplasty.