BACKGROUND/AIMS: Hirschsprung disease (HSCR) is a congenital disorder characterized by intestinal obstruction due to absence of intramural ganglion cell. RET and Endothelin-B receptor (EDNRB) gene have been shown as a susceptibility gene for HSCR. The aim of this study is to evaluate the association of the two genes with HSCR. METHODS: Mutation analysis of RET and EDNRB gene was performed in 33 sporadic HSCR patients by using single stranded confirmational polymorphism. We examined allelic frequencies at six polymorphic loci of RET by using restriction fragment length polymorphism. Allelic frequencies in HSCR were compared with those in the control populations. RESULTS: No mutation was detected in patients with HSCR. Two polymorphisms in RET, A45A (135G > A) and L769L (2307T > G) were over-represented in patients with HSCR compared to controls. In contrast, G691S (2071G > A) was under-represented in the HSCR patients. CONCLUSION: Polymorphism in the RET gene is associated with the development of sporadic HSCR.