The application of distraction osteogenesis to the membranous bones of the craniofacial skeleton and its effects on cranial volume and overall skull shape have not been fully studied. This pilot study was designed to compare distraction of a cranial suture in the rabbit model with distraction across an osteotomy and to evaluate the response of the suture both grossly and histologically. Additionally, the need for a period of rigid fixation after distraction was evaluated. Calibrated distraction of either the coronal suture or an osteotomy in the midsection of the parietal bone using an internal distractor (Synthes Maxillofacial, Paoli, Pa.) was studied in juvenile and adult New Zealand White rabbits. Skull growth and distraction were followed by serial cephalograms, and bone biopsies of the distracted sites were obtained after death for histologic evaluation. Craniometric analysis of the skulls was also performed. There was significantly greater mean marker separation in the juvenile suture distraction group (6.6 ± 0.2 mm; n = 3) than in the control group (2.2 ± 0.2 mm; p < 0.01). Marker separation was also significantly greater across the parietal osteotomy (6.4 ± 0.1 mm) than in the sham group (no marker separation). Craniometric data demonstrated the ability of the juvenile skull to distribute the change at the coronal suture throughout the skull to maintain symmetry and minimize disproportion. No distraction was obtained across the adult suture. In the juvenile suture distraction group without a period of stable fixation, a relapse of 17 ± 6 percent was noted after 1 week, an additional 2.3 ± 0.5 percent after the second week, and no further change in the third postdistraction week (n = 2; p < 0.01). These results show that in this animal model, distraction osteogenesis can be achieved across a growing cranial suture without an osteotomy or suturectomy and that the degree of distraction and new bone formation is comparable to that across an osteotomy. This suggests that cranial expansion can be obtained in a growing animal without using a more invasive cranial osteotomy. Additionally, the first week after distraction seems to be the most critical time period to maintain stable fixation.