Serum TATI (tumor-associated trypsin inhibitor) was measured in 41 control subjects, 30 patients with pancreatic cancer, 53 with chronic pancreatitis, and 47 with extrapancreatic diseases, mainly of gastrointestinal origin. TATI was found to be elevated in some subjects in all groups of patients; patients with chronic pancreatitis studied during an acute exacerbation of the disease had the highest percentage (68%) of pathological values. TATI was found to be correlated with elastase 1, tissue polypeptide antigen, and total and pancreatic isoamylase. A significant relationship was also found between TATI and serum creatinine levels.