Introduction/purpose: Surgically assisted rapid palatal expansion is used for the management of transverse maxillary deficiency in the early permanent dentition. The success depends on the maintenance of an adequate blood supply to the mobilized segments. The aim of this study was to assess the effects of corticotomy and midline osteotomy on the tooth pulpal blood flow. Material: Laser Doppler flowmetry was applied as a non-invasive and reliable technique for the assessment of pulpal blood flow in the maxillary centrals, canines and first molars. The blood flow was investigated pre- and postoperatively, on the first, third, and seventh postoperative days bilaterally in 13 cases. Results: The results of this study indicate that ischaemia of the pulp can occur following osteotomy at the Le Fort I level. Conclusion: Corticotomy 5 mm above the dental apices and separating the midpatatal suture did not have any serious effect on pulpat blood flow in this study. (C) 2003 European Association for Cranio-Maxillofacial Surgery.