Hypotonic duodenography has become a well accepted procedure for diagnosing pancreaticoduodenal cancer. In order to provide further data about the accuracy of this examination, 170 patients were reviewed who were suspected of having this disease and whose duodenogram diagnosis was later confirmed or disproved by surgery, autopsy, or clinical follow-up. The correct diagnosis was made in 158 patients (over-all accuracy of 93%). Of 31 ultimately proved pancreaticoduodenal cancers, 24 were correctly identified (specific accuracy of 77%). For 27 patients a positive diagnosis of pancreaticoduodenal cancer was made, and 24 of these later proved to have this disease (positive accuracy of 89%). For 110 patients, a negative diagnosis was made, and 103 of these proved to be free of pancreaticoduodenal cancer (negative accuracy of 94%).