The purpose of this project was to study the effect of calcium sulfate on early bony consolidation in distraction osteogenesis. In the control group, a total of 17 patients were treated between December 1997 and December 1999. The age of patients ranged from 2 to 45 years. The follow up period was 6 to 24 months(mean 15.3 months). In experimental group, a total of eight patients with craniofacial microsomia were treated between April 2000 and February 2001. The age of patients ranged from two to 40 years old. All patients were male. The follow up period was 3 to 15 months. The operative procedure in adult was based on the Ortiz Monasterio's simultaneous mandibular and maxillary distraction technique. The authors modified the original Ortiz Monasterio's method by using Le Fort I osteotomy with complete separation of both pterygomaxillary junction and mandibular osteotomy to avoid the resistance during distraction. In child, the osteotomy of the mandible was performed to distract. In the control group, in adults, after 5 days of latent period, distraction was performed at a rate of 1 mm per day. After 6 to 8 weeks of consolidation period, intermaxillary fixation and distraction device were removed. In children, the distraction was started at a rate of 1 mm per day without latent period. The consolidation period was 4 to 6 weeks. In the experimental group, after 5 days of latent period, distraction was performed at a rate of 1 mm per day in 2 adults. However, in children distraction was performed at a rate of 1 mm per day in 2 patients and 2 mm per day in 4 patients without latent period. On the completion of distraction, the calcium sulfate mixed with carboxymethyl cellulose was injected into the distracted zone. Radiographs showed bony consolidation in 4 weeks in 1 child, 5 weeks in 1 child with distraction rate of 1 mm per day, in 5 - 7 weeks in 4 children with distraction rate of 2 mm per day and in 5 weeks in 2 adults with distraction rate of 1 mm per day after injection of the calcium sulfate. The consolidation period in adult was statistically significant compared with that of the control group using Mann-Whitney U test.In conclusion, these findings suggested that injectable calcium sulfate is effective for early bony consolidation in distraction osteogenesis in adult.