We report on a patient with DiGeorge syndrome (DGS) phenotype or anomaly and an unbalanced translocation [45,XY,-10,-22, +der(10),t(10;22)(p13;q11)] resulting in monosomy of 10p13-pter and 22q11-pter. Because both regions involved in this rearrangement have been implicated in DGS, we performed a molecular cytogenetic analysis of both loci in this patient. Results indicate that the chromosome 22 DGS locus is intact but that the terminal deletion of the short arm of chromosome 10 is adjacent to or partially overlapping with the recently defined consensus deleted region observed in DGS patients with 10p deletions. We conclude that the DGS anomaly in our patient is likely to be due to haploinsufficiency of genes located on chromosome 10p. Most, if not all, of the region included in the previously described 10p smallest region of deletion overlap is not deleted in our patient. Therefore, this deletion breakpoint either narrows the previously proposed 10p region or defines a second region within 10p critical for the DGS anomaly.