The DiGeorge (DG), velocardiofacial (VCF), and conotruncal anomaly-face (CTAF) syndromes were originally described as distinct disorders, although overlapping phenotypes have been recognized. It is now clear that all three syndromes result from apparently similar or identical 22q11.2 deletions, suggesting that they represent phenotypic variability of a single genetic syndrome. We report on 12 individuals in five families with del(22)(q11.2) by fluorescent in situ hybridization, and define the frequency of phenotypic abnormalities in those cases and in 70 individuals from 27 del(22)(q11.2) families from the literature. Common manifestations include mental impairment (97%), abnormal face (93%), cardiac malformations (68%), thymic (64%) and parathyroid (63%) abnormalities, and cleft palate or velopharyngeal insufficiency (48%). Familial DG, VCF, and CTAF syndromes due to del(22) (q11.2) show significant inter- and intrafamilial clinical variability consistent with the hypothesis that a single gene or group of tightly linked genes is the common cause of these syndromes. Up to 25% of 22q deletions are inherited, indicating that parents of affected children warrant molecular cytogenetic evaluation. We propose use of the compound term "DiGeorge/velocardiofacial (DG/VCF) syndrome" in referring to this condition, as it calls attention to the phenotypic spectrum using historically familiar names.