BACKGROUND/AIMS: Due to widespread use of computerized tomography (CT) scan to examine patients with variable disease or complaints, detection of incidental or unsuspected gastrointestinal abnormalities are not uncommon. Clinical significance of incidentally detected bowel wall thickening (BWT) on abdominal CT scan is uncertain at present. Despite the necessity for the clinical guidelines describing the evaluation of incidental bowel wall thickening on CT scan, there have been few studies concerning these radiological abnormalities. Our objective was to determine whether endoscopic evaluation is necessary for the evaluation of these abnormal findings. METHODS: This study evaluated one hundred and forty patients with incidentally detected BWT on abdominal CT scan in Inje University Sanggye Paik Hospital from 2001 to 2003. 102 patients of those were proceeded by endoscopic evaluation. Forty-eight patients had received upper endoscopy, 26 patients had colonoscopy, while 28 patients had sigmoidoscopy. RESULTS: Endoscopic work up revealed significant abnormalities in 83% of patients with incidental findings of the distal esophagus, 73% of patients with thickening of the stomach, 35% of patients with thickening of the right colon, and 71% of patients with thickening of the sigmoid colon and rectum. CONCLUSIONS: Although significant pathologic findings are less common in thickening of the right colon than other bowel wall thickening, all of these incidental findings on CT scan warrant further endoscopic evaluation.