The authors report three anatomoclinical studies concerning apparently moderately aggressive endocrine tumors developped in the sub-mucosa of the duodenal bulb (2 cases) and of the pyloro-bulbar region (1 case), not connected with the pancreas, and occuring in the absence of a parietal ectopic pancreas. Two of these tumors were ulcerous but the associated syndromes (pains and hemorrhage) did not evoke, clinically, a Zollinger-Ellison syndrome. However, examination with immunofluorescence showed the presence of immunoreactive gastrine in a large number of cells. Having found some similar cases in the literature, the authors precise the features of these silent pyloro-duodenal gastrinomas: it is a variety of carcinoids or of "carcinoid-islet cell tumors". The cells contain argyrophile granules (Grimelius stain) which correspond in electron microscopy to neuro-secretory granules that may be quite different from G. granules. In the absence of significant clinical signs and of a radio-immunologic blood test, the presence of immunoreactive gastrin in the cells is the main feature for the diagnostic of these tumors. These tumors seem to arise from the gastrin cells of the mucosa or from their precursors as is suggested by the transitional forms with the fundus of the glands. Whatever the reason of the peculiar functional behavior, these neoplasms can be easily isolated from the anonymous group of duodenal carcinoids.