Irritable bowel syndrome is the most common gastrointestinal disorder. The motility disturbance determines the clinical presentation and two types are distinguished, i.e. spastic colon and painless diarrhea. The motor dysfunction is probably related to abnormal myoelectric activity of the colon. In contrast to healthy persons, slow electrical waves with a frequency of 3 cycles per minute predominate. Although irritable bowel syndrome is a disease of unknown etiology, psychological factors and fibre-deficient diet may be involved. The work-up should take into account the fact that irritable bowel syndrome remains a diagnosis by exclusion. The effect of current therapy on the chronic-relapsing course of this disease is only slight.