We measured the concentrations of trypsin, elastase, and three anti-proteases-alpha 1-macroglobulin, alpha 1-antitrypsin, and alpha 1-antichymotrypsin-in serum from 10 patients with pancreatic carcinoma. All 10 showed increased elastase and decreased alpha 2-macroglobulin concentrations, nine had increased alpha 1-antichymotrypsin, and eight had increases in alpha 1-antitrypsin and trypsin. Serial studies during chemotherapy of one patient showed that the protease concentrations decreased during treatment but the concentrations of the anti-proteases remained abnormal.