Endoscopic ultrasonography was evaluated for detection of tumors of the pancreas. The technique was performed in 42 patients with cancer of the pancreas and 8 patients with nodular fibrosis of chronic pancreatitis. The lesions were clearly identified in all 50 patients, even when the size of the tumor was less than 20 mm in diameter. A tumor of the pancreas was usually visualized as a hypoechoic mass that had a characteristic image depending on the size. Ultrasonographic differentiation of malignant from benign tumors of the pancreas was possible in tumors larger than 30 mm in size but difficult in tumors less than 20 mm in size. Compared with conventional ultrasonography, endoscopic retrograde pancreatography, computed tomography, and angiography, endoscopic ultrasonography had the highest detection rate of tumors of the pancreas, especially in cases of small tumors under 20 mm in size. In cancer of the pancreas, endoscopic ultrasonography also proved to be valuable for the detection of vascular invasion.