From 1932 through 1967, at The New York Hospital there were 64 primary duodenal tumors, 35 benign and 29 malignant. Many histologic types were found among the benign tumors. Distal to the bulb, all but one of the 26 malignant tumors were carcinomas, while none of the 3 malignant bulb tumors was of this type. Benign tumors were much more common than malignant tumors in the bulb (14:3). With respect to the bulb alone, there were twice as many males as females. Patients had an average age of 61 years, and all were white. [See figures in the PDF file] The symptoms and response to a milkalkali regimen of patients with a bulb tumor were indistinguishable from those of patients with a duodenal peptic ulcer. Polypoid intraluminal tumors were diagnosed correctly on preoperative gastrointestinal roentgenograms, and these tumors were always benign. However, there appears to be no way to differentiate the histologic types on gastrointestinal examination. Intramural tumors without a significant intraluminal component were consistently misdiagnosed as ulcer or deformed bulb. Of 6 such tumors 5 had associated ulcers at operation. After reviewing the preoperative gastrointestinal series, it is suggested that the findings of an unusually large bulb or ulcer, or a bizarre configuration such as the lucent area in Figure 5, A and B should raise the possibility of intramural tumor. Half of these intramural tumors were malignant.