Vertical distraction osteogenesis has received considerable interest as a way to augment bone prior to implant placement. However, very little is known regarding the appropriate distraction protocols in the human mandible. In this study, we evaluate the effect of the distraction rate and the duration of neutrofixation on bone formation and closure of the gap in the human mandible. Vertical distraction was performed in the atrophic mandible of 16 edentulous patients, aged 62 ± 6 years. The bone was distracted for approximately 10 mm at a rate of either 0.5 or 1 mm/day. Bone biopsies were taken after 7–20 weeks of neutrofixation. Histological analysis demonstrated newly formed bone in the distraction gap in all biopsies. The bone was predominantly of the woven type. After 10 weeks of neutrofixation, the gap was bridged by new bone in two out of three intact samples in the 0.5 mm/day group, but not in two intact samples of the 1 mm/day group. Histomorphometry revealed longer bone trabeculae (P=0.02) and a somewhat increased bone volume in the area where new bone formation started (P=0.07) in the group of patients having the 0.5 mm/day of distraction rate than in the 1 mm/day group. We conclude that in elderly patients, a distraction rate of 0.5 mm/day results in faster osteogenesis in the distraction gap than a rate of 1 mm/day. A minimum of 10 weeks of neutrofixation seems to be needed to close a 10 mm gap after cessation of distraction.