Twenty-three histologically proved cases of carcinoma of the pancreas were investigated preoperatively with endoscopic retrograde cholangiopancreatography and cytologic examination of pure pancreatic juice collected after secretin stimulation. In 12 cases in which radiology was highly suggestive of carcinoma, cytology confirmed the result in seven. When radiologic findings were equivocal, cytology was helpful in two of six cases. Cytology was most helpful in the patients in whom no diagnosis could be reached radiologically due to tumor invasion of the structures adjacent to the papilla. Malignant cells were found in all cases.