One hundred fifty-five unselected obstructive sleep apneic patients seen in succession had cephalometric roentgenograms and polygraphic recordings performed. These patients were compared to a group of 41 subjects who had consulted orthodontists for malocclusion and had no clinical indication of sleep apnea. The cephalometric landmarks were also compared to those published as normative data in the literature. The limits of "normalcy" were conservatively defined as mean +/- 2 standard deviations. Only two obstructive sleep apneic patients had normal cephalometric landmarks and 150 of the 155 patients had at least two significantly different landmarks from the normative data in the literature. The common findings were a retroposition of the mandible, a different cranial base flexure with a nasion-sella-basion angle more acute than expected, and a displacement of the hyoid bone to a lower position than expected. These combined changes reduced the space occupied by soft tissues anchored on the skull and mandible, and the length of the soft palate was increased.