A modified technique for mandibular distraction is reported: an oblique corticotomy is made in the external cortex of the mandible at the level of the gonial angle. Two intraosseous stainless steel pins are inserted and are joined by a softer distraction screw. We make two corticotomies, one horizontal and one vertical, and insert three pins to achieve bidirectional distraction when the mandibular body and the ascending ramus are hypoplasic. This procedure has been used in 87 patients with unilateral hemifacial microsomia and 19 patients with bilateral mandibular hypoplasia. A mean elongation of 19 mm was obtained in the unilateral group. In the bilateral cases a mean vertical elongation of 7.5 mm and a mean horizontal elongation of 14 mm were obtained. A great improvement of the facial asymmetry was achieved in all the patients. The follow-up in this series varies from 3 months to 3 1/2 years (mean, 19 months in unilateral cases and 12 months in bilateral cases). No relapses have been observed.