Anatomical shape of the mandibular ramus, which includes the area from the rear of the mandibular second molar to the mandibular posterior border and from the mandibular sigmoid notch to the inferior mandibular border, must be carefully considered to perform orthognathic surgery. The locations of the lingula and mandibular foramen in medial side of mandibular ramus are one of the most important factors to decide the location of the horizontal medial osteotomy in sagittal split ramus osteotomy and to select the line of vertical osteotomy in intraoral vertical ramus osteotomy. Sixty-five different Korean human dry mandibles were surveyed. All mandible have permanent dentition including complete eruption of the mandibular second molar. The locations of the lingula and mandibular foramen in medial side of the ramus were identified and following results were obtained. Anterior ramal horizontal distance from lingula was $16.13{pm}3.53mm(range:8.6{sim}24.3mm)$, anterior ramal horizontal distance from mandibular foramen was $23.91{pm}4.79mm(range: 14.1{sim}39.7mm)$, horizontal width of mandibular foramen was $2.79{pm}0.95mm(range:1.5{sim}6.1mm)$, height of lingula was $10.51{pm}3.84mm(range:3.1{sim}22.4mm)$, vertical distance from sigmoid notch to lingula was $19.82{pm}5.11mm(range:9.1{sim}35.3mm)$. From this study, the result could be used to select the location of osteotomy lines and to decide amount of periosteal elevation to avoid injury of neurovascular bundle, and to accomplish the appropriate split in Korean patients in mandibular orthognathic surgery.