Tricho-dento-osseous syndrome (TDO) is characterized by abnormal bone, hair, and tooth morphology. However, the reported craniofacial abnormalities are not well characterized. The purpose of this study was to compare the craniofacial parameters of 25 subjects affected with TDO (A) with those of 15 unaffected relatives (U). Standardized lateral cephalograms were traced and digitized. Each subject's data were compared by age and sex to cephalometric standards (Bolton, Behrents); severity was scored by standard deviations from the standard mean, and then grouped into A vs. U. All cephalograms were evaluated for frontal sinuses, mastoid pneumatization, diploe, and bone density, and cranial thickness was measured. Cranial base length (SN; NBa), cranial base angle (BaSN), and mandibular body length (GoPg) were greater in A than in U (p < or = 0.05). Both groups had longer total and lower facial heights (NMe; ANSMe) compared with normal standards. Frontal sinuses, mastoid pneumatization and diploe were visible less often in A than in U (p < or = 0.05). Parietal bone and bone at lambda was significantly thicker (p < or = 0.05) in A than in U. Variability was substantial in many measures in both A and U. The major TDO craniofacial features involve the cranial base, mandibular body length, absence of visible pneumatized mastoids, frontal sinuses and diploe, and thicker cranial bone.