The form and size of the human mandible is subject to considerable variation from the accepted normal. One of the more interesting and rewarding aspects of oral surgery is the operative correction of the Mandibular abnormalities, the category of malformation into which the mandibular deformity falls. In this study we reviewed more than 30 articles to clarify the mandibular prognathism with its effects. Conclusion: Awareness of the normal and abnormal variations of the mandibular anatomy with their causes, deferential diagnosis, prognosis and complications especially mandibular prognathism is very important for the maxillo-facial surgeon to achieve a suitable decision during treatment.