Brow dermoids are benign pediatric neoplasms. Endoscopic resection requires incisions placed within the temporal hairline, which is often difficult to reliably locate in infants. The authors studied adult and pediatric patients to define the location of the hairline in relationship to simple facial landmarks. Adult and pediatric patients who were seen in preoperative consultation for facial surgical procedures were identified and included in the study. Patients with a history of facial trauma, surgery, or congenital anomalies were excluded. Digital photographs were analyzed to measure corneal white-to-white diameter. Lines were drawn connecting the tragus to the lateral canthus and from the inferiormost aspect of the earlobe bisecting the first line (line A). The maximal distance between line A and the temporal hairline was recorded. One hundred sixteen patients met the inclusion criteria, 81 adults and 35 pediatric patients. Average age was 55.9 years in adults and 3.2 years in the pediatric group. Measurements were normalized to the corneal diameter. Average temporal hairline distance from line A was 25.0 mm in adults and 21.8 mm in the pediatric group. Hairline position was not correlated with age or sex. The temporal hairline can be reliably located relative to a line drawn from the inferior aspect of the earlobe to the midpoint of the line connecting the lateral canthus and tragus. The temporal hairline is within 30 mm of this line. When designing a temporal hairline incision in infants, it can be safely placed 30 mm or more posterior to this line to ensure a well-hidden scar.