Seventy patients presenting to the gastroenterologist with upper abdominal pain were examined by a psychiatrist to establish the presence of psychiatric disorder, illness behaviour and to record in detail their symptom pattern. The 37 patients who had no organic cause for their abdominal complaints were subdivided into those with and without psychiatric disorder. The former (21 patients) demonstrated more illness behaviour, they complained of more abdominal symptoms and their pain was both more severe and more persistent than in the patients with organic disease and those with non-organic illness who did not have psychiatric disorder. The latter group reported no symptoms of 'psychoneurosis' and should probably be regarded as a separate group if the aetiology of functional abdominal pain is to be clarified. Those with non-organic abdominal complaints who had psychiatric illness could be distinguished by the presence of three symptoms, namely depression, anxiety and fatigue. Detection and treatment of their psychiatric disorder might lead to a decrease in their symptomatic complaints and illness behaviour.