The maxillary blood flow during the first 24 h following Le Fort I osteotomy was evaluated by laser Doppler flowmetry. Pulpal blood flow was recorded from two maxillary incisors and gingival blood flow was assessed from a site slightly apical to the interdental papilla of the maxillary central incisors of 12 patients receiving Le Fort I osteotomy, nine control patients receiving mandibular osteotomy, and 10 nonsurgical control subjects without orthodontic appliances. Measurements were made before surgery and at time intervals between 0-8, 8-16, and 16-24 h after surgery. The nonsurgical controls were tested at similar intervals. Gingival and pulpal blood-flow measurements did not change over time in the nonsurgical control group. Presurgical blood-flow values did not differ between the two surgical groups. Following surgery, mean gingival (but not pulpal) blood flow was significantly lower for patients treated with Le Fort I osteotomy than for patients treated with mandibular osteotomy. Follow-up examinations revealed that one patient receiving Le Fort I osteotomy experienced loss of gingiva and bone around both central incisors. This patient had one of the largest reductions in gingival blood flow.