This study aimed to investigate pertinent arterial supplies of masseter muscle to prevent fatal hemorrhage in resection of masseter muscle and/or mandibular angle ostectomy. Fifty-three postmortem cadavers of Koreans were used for the work. Color latex was injected into the arteries to outline 17 of 53 specimens. We found that an artery branches off the external carotid artery and enters the masseter muscle at the midpoint of its posterior margin 31 mm above the gonion. We termed this the middle masseteric artery. The middle masseteric artery is divided into superficial and deep branches. The deep branch of the middle masseteric artery travels deep in the muscle close the periosteum of the mandible in 94% of cases. The average diameter is 1.23 +/- 0.26 mm. A small artery with 1.23-mm diameter is enough to cause massive bleeding if severed. The deep branch of the middle masseteric artery is vulnerable in such procedures as resection of the masseter muscle and/or ramus and angle of the mandible.