The diagnosis of 'irritable bowel syndrome' can usually already be established after history-taking and a limited physical examination, particularly if the symptoms have persisted for many years in the same form. Additional investigations are indicated in the case of diarrhoea which lasts longer than 2 weeks, especially if the patient is also severely unwell or has rectal bleeding; further investigations are also required if older patients experience the symptoms for the first time, if there is blood loss upon defecation, if unintentional weight loss occurs or if a mass is felt on the left side of the abdomen. Further investigations consist of a rectal examination, measurement of the sedimentation, haemoglobin concentration and leukocyte count, sigmoidoscopy and an X-ray of the colon. Treatment should aim to reduce unnecessary concern and avoidance behaviour, and to positively influence additional stress-inducing factors, nutrition and physical activity. Medication is not indicated except for laxatives if constipation plays an important role and if advice about nutrition and physical activity provide insufficient relief.