A retrospective study of 90 surgically treated patients with the Zollinger-Ellison syndrome seen from 1958 through 1990 was performed. Fifteen patients had Zollinger-Ellison syndrome as a manifestation of multiple endocrine neoplasia type I. Preoperative tumor localization was positive in 46% of 54 patients studied. Gastrinomas were identified in 66% of patients, 38% of the tumors being malignant. Postoperative eugastrinemia was achieved in 11% of patients after a variety of surgical procedures. Exploratory laparotomy provides the only chance for cure and identifies the significant prognostic factors associated with long-term patient survival: small tumor size, extrapancreatic primary, and absence of tumor metastases.