Background: Accessory mental foramen (AMF) is addition foramen present in the body of the mandible in addition to mental foramen. The accessory branch of mental nerve passes through it. Since many surgical procedures in oral and maxillofacial surgeries involve mental region, so knowledge of its anatomical variation is very important for the surgeon. The aim of this study was to find the incidence, location, and morphology of AMF.

Material and Methods: Study was carried out on 50 (33 male, 17 female) adult dry mandible of North Indian population in the Department of Anatomy, AIIMS Patna. Incidence, morphology and topographical relation to the teeth of the mandible and mental foramen were noted.

Result: Incidence of AMF was 10 %, all foramen were round in shape, and Average size of AMF was 1.36mm. AMF lies 3.45 mm from mental foramen. On the right side, the most common position of AMF is antero–inferior to mental foramen. The most common position of AMF in relation to mandibular teeth on the right side was below the apex of 1^st premolar in all cases while on the left side it was situated below the apex of 2nd premolar in 75%, and in between the 1^st and 2^nd premolar in 25% cases.

Conclusion: Knowledge of AMF will help the anaesthetist for complete nerve block and also for surgery in the mandibular region to prevent mental nerve injury.