Congenital central hypoventilation syndrome (CCHS) typically presents in the newborn period. A case series of five adults is presented, each heterozygous for a documented polyalanine expansion mutation in the PHOX2B gene and evidence of nocturnal alveolar hypoventilation. All cases had symptoms in childhood, but survived to adulthood without ventilatory support. After identification of physiologic compromise, artificial ventilation was initiated. These adults have the mildest of the CCHS-related PHOX2B polyalanine expansion mutations, coding for only five extra alanines; three of the adults have affected offspring. Report of these cases should lead to a more rapid identification of CCHS presenting in adulthood.