Three cases of congenital central hypoventilation syndrome (CCHS) associated with Hirschsprung's disease (HSCR) were examined with respect to their genomic DNA on the coding region of the receptor tyrosine kinase (RET) and the endothelin-B receptor (EDNRB). No causative mutations for the disease were detected, but one polymorphism was observed in exon 11 of the RET proto-oncogene. In cases with CCHS, HSCR occurs with a high incidence, and this disease complex has been described as neurocristopathy due to aberrations in neural crest cell proliferation, differentiation or migration during the early fetal period. Both the RET and EDNRB may play important roles in the modulation of neurocristopathies; however, further systemic studies in a large population of patients and control subjects are necessary for elucidating the pathogenesis of this disorder.