The present study was designed to assess the effectiveness of techniques of behavioural assessment and treatment of Crohn's disease (CD). On the assumption that stress events have a pronounced influence on the life of Crohn's patients, we proposed stress management treatment. This is intended to control stress and improve patients' personal and social competence. Forty-five patients with Crohn's disease were randomly assigned to one of three treatment groups, two experimental groups: stress management and self-directed stress management, and a control group: conventional medical treatment. The subjects underwent eight individual sessions which were specific to each condition. All subjects completed symptom monitoring diaries. The subjects who received training in stress management experienced a significant post-treatment reduction of tiredness (P < 0.1), constipation (P < 0.1), abdominal pain (P < 0.5) and distended abdomen (P < 0.5). The subjects who received training in self-directed stress management experienced a significant reduction in tiredness (P < 0.1) and abdominal pain (P < 0.5). No significant changes were observed in symptomatology in the conventional medical treatment group. Similar results were obtained in the 12 month follow-up.