We report an impressive case with Zollinger-Ellison syndrome (ZES), in which stress-induced sympathetic discharge influenced serum gastrin. Our patient was a 35-yr-old female who complained of frequent and massive vomiting (more than 4000 ml of gastric juice) which was aggravated especially by psychosocial stress. Basal hypergastrinemia (1900 pg/ml) was found after the admission. The most striking finding was that laboratory stress dramatically increased serum gastrin (from 1900 to 5400 pg/ml) and plasma noradrenaline (from 180 to 1130 pg/ml). Mental arithmetic stress further enhanced hypergastrinemia (5800 pg/ml) with a concomitant increase in plasma noradrenaline (1240 pg/ml). Neostigmine (10 micrograms/kg im) also increased serum gastrin up to 6100 pg/ml but propranolol (40 micrograms/kg i.v.) reduced these elevations (noradrenaline: 990 pg/ml, gastrin: 5000 pg/ml). In this case, the effect of stress on serum gastrin mimicked the effect of catecholamine infusion in ZES. These findings suggest that psychological stress induces serum gastrin secretion via beta-adrenoceptor with exacerbation of symptoms in some cases with ZES.