Many inherited disorders have oral manifestations which can be detected on dental radiographs as alterations in the morphology or chemical composition of the teeth. Thus the dentist may be the first to detect disorders of development and metabolism of importance to the general health of the patient and his family. In one group of conditions the pulp chamber is larger than normal. This may be associated with taurodontism in such conditions as polyploidy of the -X chromosome and trisomy-21 or Down's syndrome. Taurodontism also occurs in a variety of other syndromes including the tricho-dento-osseous syndrome described by Robinson, Miller and Worth (1966) and Mohr's syndrome. It may also be associated with scanty hair endoligodentia. In certain metabolic conditions the pulp chamber may be enlarged but the teeth are of relatively normal from (cynodont). Such cases include hypophosphatemic vitamin D-resistant and dependent rickets, pseudo-hypoparthyroidism otodental syndrome and hypophosphatasia. Small pulp chambers and associated anomalies of root morphology also occur in hereditary disorders either alone or as part of various syndromes such as dentino-osseous dysplasia and brackioskeletogenital syndrome. Dentinogenesis imperfecta may occur alone or as one manifestation of osteogenesis imperfecta. Other developmental defects including pulpal dysplasia, labodontia and dens invaginatus are also associated with small pulp chambers.