The stability of surgical maxillary advancement in a consecutive series of patients with cleft lip and palate who underwent Le Fort I osteotomy with and without simultaneous mandibular setback surgery was evaluated. Preoperative, postoperative, and follow-up lateral cephalograms of 21 patients were assessed to compare differences in surgical movement and postoperative relapse between two groups: those who underwent maxillary surgery alone and those who underwent bimaxillary surgery. Differences in the number of patients who experienced relapse of <2mm, 2-4mm, and >4mm between the groups were also compared. Mean advancement of the cleft maxilla was 5.5mm in the maxilla only group and 3.6mm in the bimaxillary group, with a mean horizontal relapse of 0.8mm and 0.2mm, respectively. Mean surgical movement in the vertical dimension was comparable in the two groups and the magnitude of vertical relapse was less than 0.4mm overall. Approximately 80% of patients in both groups experienced horizontal relapse of less than 2mm. There was no significant difference in the degree of postoperative relapse between those who had single-jaw surgery and those who had two-jaw surgery.