Study aims: to evaluate the pattern of missing teeth in families, to observe similarities and differences of dental phenotype among affected relatives, to characterize the mode of inheritance and to identify distinct groups of patients for further molecular investigations. Patients and Methods: Clinical examinations were carried out on 26 Caucasian patients from 11 families with a family history of missing teeth. Combined examination of clinical phenotypes and panoramic radiographs improved the precision of diagnosis. Family study was used to determine whether there is a hereditary basis for tooth agenesis. Results: In all families, the patients and their affected relatives did not share the same pattern of missing teeth. There were differences according to the tooth type, region, symmetry and number of teeth involved even in the same family. The most commonly missing teeth were: upper lateral incisors, second lower and upper premolars, lower central incisors, upper canines. Symmetrical hypodontia and anterior tooth agenesis were predominant. Anomalies of tooth-size and tooth-shape were observed in association with hypodontia phenotype. Conclusions: Familial isolated tooth agenesis is a genetic trait with clinical heterogeneity and autosomal dominant inheritance pattern. Schlagwörter: tooth agenesis, congenital missing teeth, familial hypodontia