This study was performed to evaluate the physiological effects of Bacillus sp. on Periplaneta americana. The insecticidal exotoxin was fractionated by ion-exchange chromatography and gel filtration from Bacillus sp. cultivates. LP$_2$ among 4 lipoproteins showed markable increase after 24 hrs, but there was no change in gly-coprotein. The enzyme activities of P. americana showed mostly decreasing pattern by treatment of exotoxin fractions. Protease activities decreased at 12 hrs after treatment in comparison with normal subjects. Amylase also showed decreasing pattern and maximal decline was observed after 12 hrs. Trehalase activities decreased at 6 hrs and 24 hrs. Invertase activities decreased from 6 hrs to 24 hrs, but recovered after 48 hrs. Amylase isozyme $A_1$ and $A_2$ disappeared and new isozyme appeared after 12 hrs with exotoxin treatment. Trehalase isozyme T$_1$ and invertase I$_4$ increased markedly after 12hrs. However, non-specific esterase El disappeared after 24hrs.