Abstract From 1977 to 1983 we used cimetidine as primary therapy for 17 patients with the Zollinger-Ellison syndrome. All patients were treated with oral doses of cimetidine, 300 to 600 mg, four times a day, unless symptoms of hyperacidity developed or until evidence of a potentially resectable tumor became available, at which time they underwent definitive therapy. Eleven (65 percent) had no response to cimetidine therapy, 7 of whom had symptomatic recurrent ulcers, 3 of whom had esophagitis, and 2 of whom had severe diarrhea. Eight of these patients were treated with total gastrectomy, two with successful tumor resection, and one with parietal cell vagotomy (which facilitated the control of hyperacidity with cimetidine). All operations except one were performed electively and there was no operative mortality.