Background/Aims : Defecation syncope is a subgroup of neurocardiogenic syncope which occurs during or immediately after defecation. The aim of this study was to evaluate the clinical characteristics of patients with defecation syncope and the usefulness of head-up tilt test (HUT) in diagnosing the defecation syncope. Methods: Forty-five patients who had a history of defecation syncope or presyncope were selected from 454 patients who underwent HUT from Oct, 1994 to Jan, 1998. Their clinical characteristics and HUT results were reviewed retrospectively. Twenty-one subjects with positive HUT were interviewed by telephone about the recurrence of symptoms after diagnosis. Results: Median frequency of defecation syncope or presyncope was 4 (range; 1-30) and 34 subjects (75.6%) out of 45 patients were females. Injury due to the events occurred in 9 subjects (20%). In 16 cases (35.6%), syncope or presyncope occurred under situations other than bowel activity. Majority of the patients (40 cases, 88.9%) had prodromal symptoms. The result of HUT was positive in 29 subjects (64.4%). Clinical characteristics of the patients showed no difference according to sex and results of HUT. Conclusions: Defecation syncope is a subgroup of neurocardiogenic syncope and the head-up tilt test can be a useful tool in diagnosing the defecation syncope or presyncope. (Kor J Gastroenterol 1999;34:601 - 608)