Eight(I through VIII) of Bowman-Birk proteinase inhibitors have been isolated from soybean with DEAF-Sephadex A-50. Inhibitor VII was a typical BBTI, showing high cysteine content(17%/mole) and low trypsin to chymotrypsin inhibiting activity(TIA/CIA=1.0) with the independent reactive site to tech enzyme. Dissociation constant of trypsin-BBTI and chymotrypsin-BBTI complexes were 9.17 × 10^(-9)M and 5.14 × 10^(-9)M, respectively. Inhibitor VII was extremely heat stable. Six hours hit treatment at 100℃ caused only 50% decrease in it`s original inhibiting activity. Except inhibitor III, 6 other isoinhibitors differed from a typical BBTI in TIA/CIA values, ranging from 3 to 29.