Abstract: The distribution and biosynthesis sites of cathepsin B in Helicoverpa armigera through the developing stages were studied by means of Immunoblot and Northern Blot.The results of Immunoblot showed that cathepsin B existed in ovary,female and male adult fat body.The mRNA in larval fat body,female pupal fat body,male adult fat body,female adult fat body and ovary were detected using Northern Blot.This indicated that cathepsin B mRNA could be transcribed in these tissues.However there was no cathepsin B mRNA in larval epidermis and larval mid-gut as also no distribution of this proteinase.Furthermore,we detected mRNA transcrip tion in larval fat body,female pupal fat body using Northern Blot,but there were no cathepsin B distributed in these two issues accordingly in Immunoblot.This indicated that the mRNA in these two tissues could not be translated into cathepsin B,and there might be some kind of regulation in translation level.