Cancer of the ampula of Vater occurs in 10% of cases of jaundice caused by malignant neoplasms. Endoscopy with biopsy and citological study helps to establish the diagnosis in most instances, utilizing a duodeno fibroscope JFB-2. Fourteen patients, ten men and four women, were studied in a five year period in the Service of Endoscopy in the General Hospital of National Medical Center of the Mexican Institute of Social Security. All the patients presented with obstructive jaundice and only in four was papilary carcinoma suspected from the clinical and radiological studies. Direct biopsy was performed in all patients and brush biopsy for citology in 9. In all 14 patients a malignant lesion was observed macroscopically in the ampula of Vater projecting in to the duodenum. In thirteen of fourteen the lesion was diagnosed microscopically as adenocarcinoma and in eight of nine citologically. The utilization of this methodology facilitates the early diagnosis of the lesion in this way improves considerably the prognosis.