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A detailed description of the anatomical relationships of the supraorbital nerve as it courses across the forehead and under the scalp cannot be found in most anatomy textbooks, and illustrations of the nerve beyond the superior orbital rim frequently misrepresent its course. Because the supraorbital nerve is a structure at risk in many plastic surgical techniques, the plastic surgeon would benefit from a clearer understanding of its anatomy and function. The supraorbital nerve was studied anatomically in 12 (24 half-head) fresh cadaver specimens, and its sensory distribution was studied in 30 living subjects using selective nerve blocks. Beyond the orbital rim, the supraorbital nerve has two consistently present divisions: (1) a superficial (medial) division that passes over the frontalis muscle, providing sensory supply to the forehead skin and only to the anterior margin of the scalp in 90 percent of the study subjects; and (2) a deep (lateral) division that runs cephalad across the lateral forehead between the galea aponeurotica and the pericranium as the sensory nerve to the frontoparietal scalp. When a forehead lift is performed, injury to this deep division causes most of the distressful sequelae of scalp numbness and paresthesia. Unlike the superficial division, the course of the deep division in all cadaver specimens and its sensory distribution in all living volunteer subjects was consistent. This, study has application for any procedure requiring scalp or forehead incisions, such as the forehead lift and the endoscopic facial techniques. With preoperative planning, scalp incisions may be placed to avoid the superficial supraorbital nerve branches and preserve the deep division of the supraorbital nerve.