One hundred and four men with the suspected diagnosis of sleep apnoea syndrome (SAS) not suffering from neuromuscular diseases or acromegaly were examined by X-ray cephalometry. Subjects suffering from bronchial obstruction, laryngeal carcinoma, suspected Treacher Collins syndrome as well as subjects in whom SAS was not verified were excluded. The remaining 81 men were divided into two groups depending upon disease severity as expressed by the mean index of oxygen desaturations per hour (less than 30-group A; more than 30-group B). In group B, the following parameters were significantly altered as compared with group A: dorsocaudal rotation of the mandible, elongation of the soft palate, and an increase of the saddle angle, increase of the angle of the cranial base, the lower gonion angle and the angle of the inclination of the mandible. Differences in the size of the soft palate, the rotation of the mandible and the size of the lower gonion angle can be found not only between healthy and subjects with SAS but also between subjects with mild and severe apnoea.