Intestinal obstruction secondary to intraabdominal adhesion is a well-known postoperative complication occurring after appendectomy. The aim of this study was to measure the incidence and clinical manifestations of mechanical intestinal obstruction after appendectomy for perforated appendicitis. We reviewed all of the children (age <16 years) who had been treated for appendicitis at Asan Medical Center between January 1996 and December 2001. Inclusion criterion included either gross or microscopic evidence of appendiceal perforation. Exclusion criteria were interval appendectomy, and patients immune compromised by chemotherapy. Associations of intestinal obstruction with age, sex, operation time, and use of peritoneal drains were analyzed. Four hundred and sixty two open appendectomies for appendicitis were performed at our department. One hundred and seventeen children were treated for perforated appendicitis (78 boys, 39 girls). The mean age was 8.9 years (range 1.5 to 14.8 years). There were no deaths. Eight patients were readmitted due to intestinal obstruction, but there was no readmission due to intestinal obstruction in patients with non-perforated appendicitis. The interval between appendectomy and intestinal obstruction varied from 12 days to 2 year 7 months. Four patients needed laparotomies. In three of four, only adhesiolysis was performed. One child needed small bowel resection combined with adhesiolysis. There was no significant association between age or sex and the development of intestinal obstruction. This was no association with operative time or use of peritoneal drain. Patients who required appendectomy for perforated appendicitis have a higher incidence of postoperative intestinal obstruction than those with nonperforated appendicitis. For the patients with perforated appendicitis, careful operative procedures as well as pre and postoperative managements are required to reduce adhesions and subsequent bowel obstruction.