The major prerequisite for resection of a pancreatic tumor is non-involvement of large blood vessels. Preoperative assessment of blood vessel infiltration may prevent unnecessary surgery. The aim of our study was to investigate the accuracy of endoscopic ultrasonography (EUS) in diagnosis of pancreatic cancer and in preoperative staging. Thirteen patients (7 females, 6 males; mean age 64 years) with a pancreatic tumor, but no evidence of distant metastases, underwent EUS and computerized tomography (CT) in order to assess blood vessel involvement by the tumor. The results were compared with intraoperative findings in 12 patients and with postmortem findings in 1 patient. A tumor was demonstrated by EUS in 12 patients and was confirmed at surgery in all 12 patients. In one patient no tumor was demonstrated by EUS, although a tumor was visible by CT; no tumor was found at surgery. In two patients CT failed to demonstrate a pancreatic tumor that was demonstrated by EUS; at surgery a tumor was detected in both patients. EUS detected blood vessel involvement in seven patients, which was confirmed at surgery in six of them. In the other six patients surgery confirmed the EUS finding of no blood vessel involvement. CT detected blood vessel involvement in two patients only. The overall accuracy of EUS and CT for detecting the tumor was 100% and 77% respectively, and for blood vessel involvement 92% and 61% respectively. In conclusion, EUS is an accurate procedure for preoperative assessment of blood vessel involvement in patients with pancreatic cancer. This procedure may enable the selection of those patients who may benefit from surgery, and should be part of the evaluation of patients with pancreatic cancer who are candidates for curative surgery.