Fluorescence in situ hybridization (FISH) analysis can reveal undetected chromosomal rearrangements. We report a patient with cleft palate, hydronephrosis, and minor dysmorphic features, including low-set posteriorly rotated ears, down-slanting palpebral fissures, mandibular micrognathia, and brachymesophalangia. Routine chromosome analysis identified no abnormality of chromosome 22; FISH analysis with the TUPLE1 probe disclosed an interstitial duplication of 22q11.2. FISH analysis did not reveal the duplication on the initial testing of metaphase chromosomes, although, on review, the area was brighter on one chromosome in each metaphase spread. FISH analysis of interphase cells showed three TUPLE1-probe sites with two chromosome-specific identification probes in each cell. Family history showed two older full siblings, a brother with behavior problems, oppositional defiant disorder, and learning problems and a sister with hydronephrosis and mild delays. The father and both siblings had similar facial features, and all three had the same interstitial duplication of the TUPLE1 probe. This family illustrates the novel complementary duplication syndrome of the velocardiofacial syndrome, which adds it to the expanding list of genomic deletion/duplication syndromes. The laboratory results further show the utility and need for careful analysis of interphase cells even in samples where good quality metaphases are available.