Bilateral mandibular hypoplasia is found in Treacher Collins syndrome, Pierre Robin sequence, and bilateral craniofacial microsomia. It causes many aesthetic and functional problems such as facial deformities with malocclusion and airway problems. We have corrected bilateral hypoplastic mandible with distraction osteogenesis, which is a highlighted method in mandibular lengthening. For last 3 years 8 months, We applied this method to four bilateral cases, where were Treacher Collins syndrome patients and bilateral craniofacial microsomia patient in rapid multidirectional fashion. A complete ostectomy was made at angle of the mandible and the mandible was fixed 5 days after lengthening was started serially 1mm every 12 hours. After consolidation period for one to three month, the device was removed. We have distracted the mandibles in vertical plane, left.18.8mm, right. 13.4mm, in horizontal plane, left 13.9mm, right 13.7mm on the average. We could achieve good aesthetic results, and their airway problems were improved without any complications.