Perioperative data on 87 patients undergoing pancreatoduodenectomy for periampullary tumors were correlated with pathologic study of operative specimens to identify the accuracy of diagnosis and the factors affecting survival. Accuracy of endoscopic retrograde cholangiopancreatography and computed tomography in locating lesions was 75% and 44%, respectively. Histologic diagnosis before or at the time of resection was available in only 61% of the patients. Carcinoma was correctly diagnosed clinically by the pathologist or the surgeon in 95% (83/87) of patients with 4 patients found to have benign disease on final pathologic examination. Intraoperative diagnosis of site of origin was incorrect in 18% (16/87) of patients. In 28% (23/83) of patients, pathologists identified nodal metastatic disease missed by the surgeon. Survival correlated with nodal and margin status and tumor grade. Tumor size demonstrated no predictive capacity. Although preoperative diagnostic accuracy is less than optimal, surgeons can usually diagnose malignant lesions but more often fail to identify tumor origin and nodal disease. We continue to advocate resection for patients with periampullary lesions thought to be malignant and resectable without a positive histologic diagnosis.