Objective : This is to report the criteria of success of intraoral distraction osteogenesis for alveolar augmentation in the severely atrophied alveolar defects through clinical result of 2 cases. Subjects and Methods : Anterior segmental osteotomy was performed and alveolar distractors (Martin and Leibinger, Germany) were applied each in 2 patients with severely defected anterior maxillary area. The osteomized alveolar segments were distracted by 1mm a day after latency period. After the consolidation period implants were installed with removal of distractor. The implants were evaluated clinically and radiographically. Results : In Case I, the distracted bone was directed to the palatal side, and another augmentation treatment - block bone graft, guided bone regeneration - was needed. In Case II, the successful alveolar bone augmentation was achieved. Dental implant was placed on distracted alveolar bone, and showed good osseointegration and good function without any complication. Conclusion : Distraction osteogenesis can be a good choice for alveolar ridge augmentation of severely atrophied ridges. However, the anterior esthetic prosthetics relies on the control of the vector, the kind of distractor, the healing capacity of patient and the etiology of atrophy. Therefore another study of each category would be needed.