Women with symptoms indicative of irritable bowel syndrome who had not consulted a physician were compared with female patients at a gastroenterology clinic to investigate whether self-selection for treatment accounts for psychologic abnormalities in clinic patients' with irritable bowel syndrome. Two sets of diagnostic criteria were compared: restrictive criteria based on the work of Manning and conventional criteria (abdominal pain plus altered bowel habits). Lactose malabsorbers were included as a control group because they have medically explained bowel symptoms similar to those that define irritable bowel syndrome. Thus they control for the causative effects of chronic bowel symptoms on psychologic distress. Women who met restrictive criteria for irritable bowel syndrome but had not consulted a physician had no more symptoms of psychologic distress on the Hopkins Symptom Checklist than asymptomatic controls. However, medical clinic patients with both irritable bowel syndrome and lactose malabsorption had significantly more psychologic symptoms than asymptomatic controls or nonconsulters with the same diagnoses. Individuals who met only the conventional criteria for irritable bowel syndrome reported more psychologic distress than controls, whether or not they consulted a physician. These results suggest that (a) symptoms of psychologic distress are unrelated to irritable bowel syndrome but influence which patients consult a doctor and (b) conventional diagnostic criteria identify more psychologically distressed individuals than do restrictive criteria.