It has been known that the retromolar foramen is a rare anatomic variation observed in the retromolar triangle, a small triangular shaped region posterior to the mandibular third molar. Due to the neurovascular bundle passing through the retromolar foramen, this anatomical structure must be kept in mind during surgical approaches regarding the retromolar area and mandible. Therefore, the authors investigated the morphology of retromolar triangle and the existence and location of retromolar foramen in Korean. And these results were compared with that of other races. We used 308 sides of 154 Korean dry mandibles, unknown gender and age. The retromolar triangle presented predominantly a triangular shape(84.1%), and the maximum height and width were 13.7 mm and 7.1 mm, respectively. In 144 of the 308 sides, the retromolar foramen was observed(46.8%). The existence of the retromolar foramen was seen the same frequency in both sides, and based on a midsagittal line of the retromolar triangle, the retromolar foramen located in more buccal side (75%) than lingual side. The mean distance between the retromolar foramen and the distal edge of the last tooth were found to be 10.3mm and 6.9 mm, respectively for the second and third molars. According to the present study, the northeast Asians including Korean population show the highest rate of the incidence of the retromolar foramen than other races. The findings suggest that practitioners should take the retromolar foramen into account in surgical procedures involving the retromolar area to protect the patient from the complications such as bleeding or nerve damage.