The purpose of this study is to clarify a pattern of the temporal branch of the facial nerve in the upper orbicularis oculi muscle (OOM) and an impact in exploiting the frontalis myofascial advancement flap. The authors investigated the pattern of the temporal branch of the facial nerve in the upper OOM in 20 cadavers. The highest and lowest level of the nerve coursing into the OOM were measured at three different sagittal/vertical planes through the lateral canthus, midpalpebral fissure, and medial canthus, respectively. The authors designate a hazard zone that delineates a circle with 1.0-cm diameter and its center located inferiorly and laterally in the direction of -15 degrees 7.5 cm from the lateral canthus. The highest level of the those twigs that entered OOM on the X-axis and Y-axis with the origin of lateral canthus is +2.51 +/- 0.23 cm, +2.70 +/- 0.35 cm, and the lowest is 0 cm, +2.68 +/- 0.32 cm, respectively. The highest level of the those twigs on the Y-axis with the origin of lateral canthus, mid-palpebral fissure, and medial canthus is +3.47 +/- 0.27 cm, +3.49 +/- 0.45 cm, and +2.97 +/- 0.35 cm, and the lowest is +1.62 +/- 0.12 cm, +1.82 +/- 0.17 cm, and +1.63 +/- 0.22 cm, respectively. Those twigs of the temporal branch of the facial nerve coursed horizontally along the fibers of OOM with interconnections but did not cross over the superior orbital rim. The authors describe details of the temporal branch of the facial nerve in the OOM and designate a hazard zone, wherein the temporal branch should be spared. They also assure that injury of the temporal branch of the facial nerve is inevitable in the procedure of the frontalis myofascial advancement flap.