The concentrations of pancreatic amylase, immunoreactive trypsin, and immunoreactive pancreatic specific trypsin inhibitor have been studied in serum drawn from 258 patients before an endoscopic retrograde cholangiopancreatography (ERCP) examination, in which both ducts were successfully filled. The results are correlated to the morphology of the ducts and the diagnosis given at the ERCP examination. One third of the patients with normal morphology of both ducts showed an abnormal concentration of at least one of the measured specific pancreatic proteins. Sixteen out of 38 patients with changes suggestive of chronic pancreatitis and 6 out of 23 patients with changes suggestive of pancreatic cancer showed normal levels of all variables measured. The sensitivity and specificity for pancreatic disease evident by ERCP were around 0.40 and 0.80, respectively, for all three proteins.