Twenty-four cases of duodenal adenomas which did not originate at the ampulla of Vater are discussed. The radiographic and clinical features of these lesions are presented together with a review of 120 cases previously reported in the literature. The role of barium studies and endoscopy in the evaluation of these adenomas is emphasized. A diameter of more than 5 cm represents a criterion favoring malignant degeneration of such non-Vaterian adenomas.