Lactoferrin as assayed by a radial immunodiffusion technique was studied in pure pancreatic juice collected at endoscopic retrograde cholangiopancreatography from 23 patients with chronic pancreatitis, 12 with acute pancreatitis, 21 with pancreatic cancer, and 29 cases of nonpancreatic gastrointestinal disease. No clear difference between lactoferrin concentrations in the chronic pancreatitis patients and other groups was found. Moreover, most lactoferrin levels were below the limit of detection in our assay. In addition, lactoferrin total protein ratios did not appear to be of value in the differential diagnosis of chronic pancreatitis. These results seem to be in contrast to the findings of other authors, who measured lactoferrin in duodenal fluid--which is unreliable, in our opinion--or who mainly studied chronic pancreatitis patients and few other pancreatic diseases. Lactoferrin might well be a nonspecific marker for serious pancreatic inflammation.