This study examines the microsurgical anatomy of the aberrant superior laryngeal artery (ASLA) which passes through the thyroid foramen. It defines the location of the ASLA and its main branches. The aberrant superior thyroid artery was looked for in 20 randomly selected Chinese adult cadavers, and when found, was dissected and measured under an operating microscope (7-30x magnification). The ASLA passed through the thyroid foramen, which only occurred in the presence of the artery. The foramen was observed in six of the 20 cadavers: one on the right, three on the left, and two on both sides. The study provides detailed information concerning the ASLA, which we hope will help explain the arterial bleeding that may occur during laryngeal surgery. The results might be helpful in improving surgery to the larynx and other neck operations. Incidental intraoperative injury of the aberrant artery could be avoided by understanding details of its course in relation to surrounding anatomic landmarks.