A 3.7 kb NdeI fragment (Min et al.,1986,Korean Biochem. J.19, 363) carrying the, insecticidal crystal protein gene of B. thuringiensis subsp. kurstaki HD-73 was recloned under the tac promoter in pDR540, the E. coli expression vector. The 130-Kdal crystal protein expressed in E. coli was very stable and amounted to about 30% of the total cellular protein under optimal conditions, and most of them are contained in the inclusion body.