A primary hepatic gastrinoma found in a 13-year-old boy was studied by light microscopy, immunohistochemistry, electron microscopy, and immunoelectron microscopy. Results were consistent with a neuroendocrine neoplasm with abundant gastrin-immunoreactive cells. Unlike all previously reported cases of primary hepatic neuroendocrine tumors, which have been endocrinologically asymptomatic, the patient had a Zollinger-Ellison syndrome apparently cured by surgical resection of the tumor.