Horizontal alveolar augmentation by distraction osteogenesis is an alternative method for reconstructing atrophic alveolar bone. A 65-year-old woman with atrophy of the alveolar rim in the anterior lower jaw, which had inadequate width for implant placement, was presented. Under general anesthesia, vertical and horizontal osteotomies of the buccolabial cortical bone were performed in the canine regions bilaterally. Modified horizontal distraction devices were stabilized to the mandible. Distraction proceeded from the seventh postoperative day at a rate of 0.450 mm twice a day for 6 days. After 3 months, distraction osteogenesis occurred and increased the alveolar width from 2 to 7 mm. Two implants were placed in the distracted areas. Marginal bone resorbtion around the implants was not observed 12 months after implant placement.