Seventeen patients with craniofacial synostosis (CFS) have been treated at the Department of Plastic and Reconstructive Surgery at Osaka Medical College during the past 10 years. Six patients were thoroughly evaluated at the Department of Otolaryngology by polysomnography (PSG), cephalometric X-ray and nasopharyngoscopy during sleep. In 4 of the patients PSG showed obstructive sleep apnea syndromes (OSAS). Heavy snoring without apnea and paradoxical respiration were noted in the other 2 patients. Thus, all of the patients had sleep-related breathing disorders (SRBD). It is assumed that the incidence of SRBD in CFS is high. Cephalometric analysis and profilogram showed maxillomandibular hypoplasia in each patient, and it was assumed that the main cause of SRBD in CFS was stenosis of the upper airway tract caused by maxillo-mandibular hypoplasia. Nasopharyngoscopy was performed during sleep in 2 patients with OSAS secondary to CFS. One patient with adenotonsillar hypertrophy had nasopharyngeal obstruction and another patient whose posterior airway space (PAS) on cephalometric radiograph was 3 mm (normal value: 11 mm) had obstruction at the tongue base.