Zollinger-Ellison syndrome is being detected at an earlier stage through liberal use of serum gastrin testing and application of secretin provocative tests if needed. The peptic ulcer disease of patients with Zollinger-Ellison syndrome can usually be controlled by large doses of one of the new potent gastric acid inhibitors. A battery of preoperative localizing tests can then be applied to guide exploratory laparotomy in non-MEN I patients. The tumor should be resected if possible, and continued low gastrin levels after operation provide evidence of a complete resection. It is reasonable to perform a parietal cell vagotomy at celiotomy because it will facilitate control of acid secretion if tumor resection is not successful. The only need for total gastrectomy is in a few patients whose acid secretion cannot be controlled with H2 receptor antagonists or who cannot comply with medical therapy. When no tumor is found at celiotomy, the prognosis for long-term tumor-free survival is excellent. Unfortunately, if unresectable hepatic metastases are present at operation, the patient is likely to die from metastatic tumor.