The condition characterized by long-standing or intermittent upper abdominal pain despite absence of structural pathological findings was studied in 40 patients. Thirty-four control patients with long-standing, well-defined orthopedic diseases were studied in parallel together with 10 healthy controls. Fifty-five per cent of the abdominal pain patients versus 12% of the orthopedic controls had aggravation of symptoms in association with at least 1 of 14 events listed in a self-administered questionnaire. Forty per cent versus 6%, respectively, had experienced outbreak of symptoms in association with at least one of the events. Besides, they viewed themselves as living under a high time and performance pressure to a significantly higher extent than the controls. During experimentally induced stress (mental arithmetic) the increase in blood pressure and pulse rate were significantly more pronounced in the group of healthy controls than in either of the two other groups. The abdominal pain patients had the smallest increase. Calf blood flow measurements were not very informative. Plasma adrenaline and noradrenaline were measured in some of the subjects. Adrenaline concentrations were generally higher in the group of healthy controls than in either of the other two groups. It is concluded that the experience of life strain plays a role for the occurrence of symptoms in patients with chronic upper abdominal pain. They seem to have a generalized suppressed autonomic reaction to stress; this may contribute to a disturbed gastrointestinal function.