We report the immunohistochemical and ultrastructural features of a case of duodenal carcinoid (somatostatinoma) combined with cutaneous-type von Recklinghausen's disease in a 65-year-old woman. The duodenal tumor located at the 2nd portion was composed of tumor cells arranged in a trabecular, glandular or nest-like pattern, occasionally associated with eosinophilic globules in the glandular structures. The tumor cells mostly showed strong immunoreactivity with anti-somatostatin antibody. Electron microscopy revealed that every tumor cell contained intracytoplasmic granules with electron-dense cores, 100-300 nm in size, in varying numbers, and intracytoplasmic lumina were rarely detected. The present case including identical cases reported so far suggest that the disease entity is likely to be a combination of duodenal somatostatinoma and von Recklinghausen's disease and/or phaeochromocytoma. This is the tenth case of duodenal carcinoid associated with von Recklinghausen's disease and/or phaeochromocytoma in the world literature and the third case reported as duodenal somatostatinoma.