Novel tripeptide derivatives having a pyroglutamic acid residue strongly inhibit a plurality of trypsin-like serine proteases such as plasmin, thrombin, trypsin, kallikrein, factor Xa and urokinase. The compounds of the present invention can inhibit various trypsin-like serine proteases and are expected to show remarkable effects as novel protease inhibitors for the treatment of pancreatitis, inflammantion, ulcer, etc.