Three cases of duodenal myogenic tumor are described in detail. All the three were surgically treated and the final diagnoses were histologically established. The three consisted of two leiomyomas and one leiomyosarcoma. To make clinical diagnosis, roentgenologic, endoscopic, and angiographic examinations were empolyed. The selective angiography was more reliable than endoscopic biopsy to make a differential diagnosis whether a tumor was benign or malignant. Surgical procedures were required not only for malignant myomatous lesions but also for benign lesions because the latter also produce a high incidence of hemorrhage from ulceration of the tumor. Out of the three cases, one was successfully treated by enucleation but the other two were undergone more extensive surgery such as a Whipple's procedure or wide resection of the duodenal wall with side-to-side duodenojejunostomy. Operative techniques are discussed in detail basing on the biological characteristics, location, and size of the tumor.