In this cluster analysis of out-patients with irritable bowel syndrome (IBS) we described the psychological features and personality patterns of these patients. The Minnesota Multiphasic Personality Inventory (MMPI) was administered to 29 IBS patients who received treatment in the gastroenterology department of Ajou University Hospital to produce individual profiles for each patient. The 29 profiles with 13 standard scales, 15 content scales and 11 personality scales were subjected to cluster analysis resulting in three clusters of the original sample. Titles used to describe the psychological features and personality patterns seen in the three clusters included : (1) depression and anxiety : (2) somatization and denial of affect ; (3) anger overcontrol. Future studies on the treatment of IBS patients may well consider these features, as IBS patients have different psychological patterns.