The 22q11.2 deletion has been identified in the majority of patients with DiGeorge syndrome (de la Chapelle et al., 1981; Kelley et al., 1982; Scambler et al., 1991; Driscoll et al., 1992a), velo-cardio-facial syndrome (VCFS) (Driscoll et al., 1992b, 1993) and conotruncal anomaly face syndrome (Burn et al., 1993; Matsouka et al., 1994) and in some patients with autosomal dominant Opitz G/BBB syndrome (McDonald-McGinn et al., 1995; Fryburg et al., 1996; LaCassie & Arriaza, 1996) and Cayler cardiofacial syndrome (Giannotti et al., 1994; Bawle et al., 1998). These diagnoses were originally described as individual entities by a number of subspecialists who were concentrating on one particular area of interest. For example, Dr. Angelo DiGeorge, an endocrinologist, first reported the combination of hypoparathyroidism and immune deficiency in children and this syndrome later came to bear his name. However, those syndromes are now collectively referred to by their chromosomal etiology – the 22q11.2 deletion. This phenomenon was previously likened to the old adage of a group of nearsighted veterinarians trying to identify an elephant by each examining a separate part (Figure 11.1). Each person was accurate in describing his own area of interest, but none was able to see the big picture. So too is the case with the 22q11.2 deletion. It was not until Fluorescence in situ hybridization (FISH) studies were available and we could identify a submicroscopic deletion in these patients that the etiology of the previously described separate entities was elucidated.