In view of the different modes of inheritance and the different prognoses of the two oro-facio-digital syndromes, type 1 (OFD-I) and type 2 (OFD-II), it is important to establish a correct diagnosis in these patients. In this report two new patients with the OFD-I syndrome are presented. One of them (Case 1) had multiple congenital malformations and never made any mental contact. She died at the age of four months and autopsy of the brain revealed abnormalities typical of the syndrome, which are discussed. The other patient (Case 2) has so far had normal mental development. Although these two patients were affected to a very different degree, they both presented the clinical and radiological characteristics of the OFD-I syndrome. These two patients and previously reported cases of the OFD-I and OFD-II syndromes were compared with a patient with the OFD-II syndrome (Case 3), a patient reported earlier who is undergoing follow-up. The radiological features of the skeleton in the two syndromes are presented. The irregular mineralization of the hands and feet characteristic of OFD-I, but not of OFD-II, seems to offer a good opportunity to distinguish between these two syndromes. It is suggested that this finding is pathognomonic for the OFD-I syndrome.