Obstructive sleep apneas syndrome (OSAS) has been associated with a clinical reduction of the pharyngeal spaces. To define whether predisposing skeletal craniofacial conditions exist in OSAS patients, 32 OSAS adult patients were compared in a cephalometric investigation with a control sample of 40 adults with ideal dentofacial traits. A t-test assessed the statistical significance of the differences in the two groups; correlation matrix tabulation and discriminant function analysis helped in the identification of the influence of different variables in segregation of the two populations. The following observations were made: There were no differences in maxillary or mandibular prognathism between the two groups. The sagittal dimension of the cranial base was significantly reduced in the OSAS sample, as was the bony pharyngeal opening and maxillary length. This posterior facial compression was associated with increased lower face height (p less than 0.01 in all cases). There were significant correlations in both groups between cranial base length or angulation and pharyngeal opening (p less than 0.01). Eighty percent of the population was correctly sorted out using the discriminant function analysis, with only eight controls and five OSAS patients misclassified. However, this analysis suggested that factors other than the cephalometric may be involved in OSAS.