Secretin provocation test in the diagnosis of Zollinger-Ellison syndrome. The secretin stimulation test has become the preferred provocative test in suspected cases of Zollinger-Ellison syndrome. A pure secretin preparation, a gastrin-specific radioimmunoassay, and an appropriate sampling sequence are important for the proper interpretation of this test. Gastric acid analysis is necessary in the assessment of hypergastrinemia to confirm acid hypersecretion and exclude achlorhydria. When properly performed and interpreted, the secretin provocation test offers a safe, expeditious, and reliable means of evaluating patients with hypergastrinemia. 