One hundred fifty-four of 184 consecutive patients diagnosed as having the irritable bowel syndrome were followed for an average of 29 months. Diagnosis was based on history, physical examination, and sigmoidoscopy. Seventy-eight percent of the patients had some form of gastrointestinal radiologic investigation, the majority ordered by the referring physicians. Treatment was restricted to reassurance, explanation, and a high-fiber diet. Twenty-five patients continued to take or had prescribed by their family physicians antispasmodics, minor tranquilizers, or laxatives. Eleven patients required psychiatric referral or major psychotropic medication. At follow-up, 79% felt their symptoms were better, much better, or gone completely. Outcome was not affected by identified psychiatric problems. During follow-up, an organic cause for symptoms was identified in six patients. The change in diagnosis was the result of clinical suspicion plus failure to respond to conservative therapy.