Congenital diaphragmatic hernia is a developmental abnormality due to failure of the normal formation of the diaphragm. While the majority of cases are idiopathic, chromosomal abnormalities have been implicated in approximately 15% of cases. Several recent series have suggested that 15q24-26 is critical in normal development of the diaphragm. We present a patient with a karyotype of 46, XX, del (15)(q26.1) born with a diaphragmatic hernia, coarctation of the aorta, and dysmorphic features. This patient represents the smallest isolated chromosomal aberration on distal 15q reported to date. The DNA regulatory proteins, myocyte-specific enhancer factor 2 proteins (MEF2), play a critical role in the control of muscle differentiation and development. One member of this gene family, MEF2A, maps to 15q26. We propose that this region is a candidate locus for diaphragmatic hernia and future investigations should examine the role of MEF2A in diaphragm formation. © 2003 Wiley-Liss, Inc.