BBPI contents in domestic soybean and soybean products were investigated by the measurement of chymotrypsin inhibiting activity(C.I.A) and competitive ELISA method. In order to produce polyclonal antibody, BBPI was purified from soybean trypsin-chymotrypsin inhibitor by ion exchange chromatography and electrophoretic gel slicing. Rabbit anti-BBPI polyclonal antibody was produced with the purified BBPI as immunogen. This antibody showed relatively specific binding to BBPI and then used for the establishment of competitive ELISA method to measure BBPI contents in extracts of soybean and soybean products. The standard curve for the measurement of BBPI in soybean extracts was drawn up within the range 0.03 to 30 ㎍/㎖ of BBPI. The C.I.A. and BBPI contents of 12 soybean cultivars were 8,462∼12,428 U/g and 482∼692 ㎎%, respectively. The C.I.A. and BBPI contents were not detected in most of soybean products except soybean sprouts, which contained 10,695∼13,249 U/g of C.I.A. and 529∼803 ㎎% of BBPI.