Enterocolitis is still the main source of mortality and morbidity in Hirschsprung's disease (HD). Between 1976 and 1993, 79 (26%) of 302 Hirschsprung patients proved to have Hirschsprung-associated enterocolitis (HAEC). Mortality was 7.6 percent (6 patients). HAEC patients, those who died of HAEC and those without HAEC were analyzed for differences in 34 parameters. The length of the aganglionic segment was found not to be a risk factor for HAEC, but early diagnosis and prompt treatment were found to decrease the occurrence of preoperative HAEC. Although we defined HAEC as foul-smelling, explosive diarrhea, some other symptoms and signs, such as abdominal distention on physical examination, vomiting, dehydration, and a history of nonspecific diarrhea were encountered with significant frequency. None of the patients had Down's syndrome. Sepsis was detected in all of the patients who died of HAEC. The severity of HAEC did not increase with the number of attacks of HAEC, and mortality was greater in the first three attacks. Differences in results between some series seemed to be related to differing definitions of HAEC.