Postoperative transient elevations of serum pancreatic secretory trypsin inhibitor are reported for the first time. The elevations were independent of the surgical procedures or sites, and the maximum serum pancreatic secretory trypsin inhibitor was seen on the 2nd to 4th postoperative day. The elevation of pancreatic secretory trypsin inhibitor was significantly correlated with the length of the operation time and the volume of blood loss during the operation. The change of serum pancreatic secretory trypsin inhibitor was also significantly correlated with those of white blood cell count, alpha 1-antitrypsin, and fibrinogen.