Salivary gamma-glutamyl transferase (GGT) activity was measured in 116 patients with several diseases that involved the hepatobiliary tract, pancreas, and miscellaneous disorders and in 20 normal subjects. We have found significantly elevated values of salivary GGT in cirrhosis of the liver (8.3 +/- 0.9 [mean +/- SEM] units/L), hepatic tumors (10.4 +/- 1.3 units/L), acute cholecystitis (18.3 +/- 2 units/L), acute pancreatitis (15.1 +/- 2.4 units/L), diabetic ketoacidosis (11.6 +/- 1 units/L), and Sjögren's syndrome (19.6 +/- 4.8 units/L). Salivary GGT activities were unmodified in fatty liver, infectious hepatitis, silent cholelithiasis, and mumps. Several mechanisms explain high salivary GGT activity. Measurement of salivary GGT activity in internal medicine merits further investigations to determine its potential diagnostic value.