Cephalometric analyses were performed on five caucasian patients with AHPS to further investigate the craniofacial abnormalities observed in this disorder. The study included four females and one male ranging in age from 11 to 33 years. Analysis of twenty-two angular and linear relationships measured on lateral cranial radiographs demonstrated the following significant abnormalities: microcephaly, short anterior and posterior cranial base, mid-face retrusion and decreased vertical face height. The sella turcica, reported as being displaced in previous studies, was normal in configuration and position in all our cases. In addition, despite the fact that four of our five patients appeared clinically prognathic, all had normal mandibular length, width and shape. It was concluded that this relative prognathism was caused by upward and forward rotation of the mandible as a consequence of the shortening and retrusion of the mid-face. We postulate that these abnormalities, responsible for the characteristic craniofacial configuration in patients with the AHPS, result from the shortening of the anterior cranial base which is secondary to abnormal brain morphogenesis and growth.