Effects of the five fermenation media on the growth and the production of endotoxin of twenty-five Bacillus thuringiensis isolates were investigated. Among the five different media, the growth and the production of endotoxin of B. thuringiensis were highest in the M4 and M5 media containing high amounts of nitrogen and carbohydrate. But the production of endotoxin was highest in the M1 and M3 media containing high amounts of nitrogen sources limiting carbohydrate. The average number of endotoxin and growth(O.D.) in the M1 and M3 medial were 4.4*107/ml and 2.42 in M1 medium and 1.3*107/ml and 1.46, respectively.