Among 302 Hirschsprung patients diagnosed between 1976 and 1993, 213 patients who had undergone definitive operations for Hirschsprung's disease (HD) were reviewed for the occurrence of postoperative Hirschsprung-associated enterocolitis (HAEC). The role of 42 parameters were analyzed. We detected 34 patients (14.0%) with postoperative HAEC with no mortality. In nine patients (26.5%) HAEC persisted postoperatively but no effect of preoperative HAEC on postoperative HAEC was detected. The length of the aganglionic segment did not have any effect on HAEC. Down's syndrome was not present in any of our patients with HAEC. Enterocolitis appeared after Swenson, Duhamel and Boley operations in 23, 10 and one patient, respectively. The incidence of HAEC was inversely proportional to age and weight at the time of definitive operation. The presence of colostomy before or during definitive operation had no effect on postoperative HAEC. Complications of definitive operations, including stricture, did not have any effect on HAEC.