Dose-response curves, time course, pH dependence and temperature sensitivity of proteolytic activity are presented for the coelomic fluid of untreated (CF) and stimulated (CFst) earthworms (L. terrestris). Proteolytic enzymes were observed in four fractions after HPLC gelfiltration and DEAE-ion exchange chromatography in CFst. Eight proteases of different electrophoretic mobility were identified after native PAGE and gelatin-agar overlay. The ability of proteolytic fractions to react with specific protease substrates Suc-Ala-Ala-Pro-Phe-thiobenzyl-ester (SPT) and N-benzylcarbonyl-ester (BLT) shows their chymotrypsin- and trypsin-like character. The occurrence of an increased number of proteases after stimulating the earthworm's coelomic cavity where leukocytes reside is discussed.