p53 gene mutations play an important role in the pathogenesis of pancreatic carcinomas. Anti-p53 antibodies and p53 protein have been detected in the sera of patients with pancreatic carcinomas. However, very little is known about the clinical significance of these p53 antibodies. We investigated the relationship between anti-p53 antibodies and the presence of p53 protein in cancer cells and the serum, as well as other clinical factors. Anti-p53 antibodies were detected in 19 (23%) of 82 pancreatic-duct-cell carcinomas, and in one (5%) of 21 cases of chronic pancreatitis. However, no antibodies were detected in mucin-producing tumors or in islet-cell tumors of the pancreas. The anti-p53 antibodies were detected in both early and advanced stages. In those patients undergoing surgical resection for pancreatic duct-cell carcinomas, the prognosis of patients who were negative for the anti-p53 antibodies was better than patients who were positive. Of the 11 cases that were positive for anti-53 antibodies, 8 (73%) were also positive for the immunohistochemical expression of p53 protein in cancer cells. However, there was no significant correlation between the presence of anti-p53 antibodies and the serum p53 protein levels. These results suggest that the benefits of measuring the anti-p53 antibody titier as a screening test to detect pancreatic carcinoma are limited, but the presence of anti-p53 antibodies predicts a poor prognosis for postoperative pancreatic carcinoma patients.