Twenty patients with irritable bowel syndrome (IBS) were randomly assigned either to intensive, individualized cognitive therapy (10 sessions over 8 weeks) or to 8 weeks of daily gastrointestinal (GI) symptom monitoring. Pre- to posttreatment evaluations showed significantly (p = .005) greater GI symptom reduction for those receiving cognitive therapy than for those in symptom monitoring. At posttreatment, 80% of the cognitive therapy group showed clinically significant improvement, whereas only 10% of the monitoring group showed this. Results held up well at a 3-month follow-up. Within the cognitive therapy group, GI symptom reductions correlated significantly with increases in positive and reductions in negative automatic thoughts.