To clarify the difference in the protein composition of pancreatic juice between patients with pancreatic cancer and normal controls, the proteins of pure pancreatic juice from three cases of cancer of the head of the pancreas and six apparently healthy adults were analyzed by two-dimensional gel electrophoresis (two-DE) followed by silver staining. Two minor proteins of Mr 59,000 and Mr 78,000 present in all the three patients were not detected in the six controls. We have identified the minor proteins with Mr 59,000 and Mr 78,000 as al-antitrypsin and transferrin, respectively, using Western blotting with antiα1-antitrypsin and anti-transferrin antibodies. In addition, serum albumin also identified by antibody binding was abundantly present in patients compared to controls. The increase in the amount of serum albumin in the patient was also confirmed by a quantitative analysis using SDS-PAGE and gel densitometry. The data indicate that not only serum albumin but also al-antitrypsin and transferrin are increased in the pancreatic juice of the patients with pancreatic cancer, as compared with apparently healthy adults. The data also suggests that the analysis of pancreatic juice proteins by two-DE with silver staining is useful for the diagnosis of pancreatic diseases. © 1986 The Japanese Society of Gastroenterology.