Leveling colostomy with a frozen-section biopsy in a Hirschsprung's disease is an important factor for a successful procedure. Two neonatal cases of Hirschsprung's disease in the descending colon are reported. In both cases, loop ileostomy was established because of the unavailability of frozen-section biopsy on an emergency basis. At the time of definitive procedure of the first case, transition zone at the splenic flexure was noted and was compatible with the frozen section biopsy. In the second case, an unexpected longer resection at a higher level than transition zone was required because of the poor vascularity after dissection. In conclusion, a leveling colostomy should be selected as a choice in long-segment Hirschsprung's disease. Confirming preservation of the marginal artery of Drummond is particularly important in case of Hirschsprung's disease in the descending colon.