Venom of A. halys blomhoffi was absorbed on a DEAE-collulose column at pH 7.0 (0.005[image], acetate buffer), and proteinases a, b and c were eluted with the buffers at the concns. of 0.005 - 0.1, 0.2 and 0.4 [image], resp. Rechromatography separated a to 2 fractions, but not b and c; a, b, and c were activated by Ca2+ or Mg2+, and were inhibited by EDTA and some bivalent metallic ions. Proteinase activity of a for casein was lower than that of b or c. Thermostability was a>b c. Opt. pH''s were detd as; a 10.5, b 9.8, and c 8.9. Cysteine or glutathione inactivated a and c, but not b, and c was completely inactivated by preincubating with cyteine. Activity of contaminating peptidases in the a, b, and c, preparations differed from one substrate to the others.