The surgical treatment of maxillo-mandibular malformations accompanying cases of hyperdivergence should aim at achieving good function for the patient by increasing space available for the tongue to move in and for proper respiration to take place and by reducing the tensions affecting muscles and ligaments either by dis-inserting them or by moving skeletal structures in the direction that muscles attached to them contract. An analysis of the literature shows that by respecting these principles surgeons can obtain good results in the majority of cases even in instances of extreme deficiency of the body of the mandible or where lengthening of the ascending rami is required. For these patients a cooperative effort of the surgeon and the orthodontist becomes even more than ever indispensable. In addition it will be necessary for the treatment team to follow these patients for an extended post-operative period.