The present study was planned to elucidate the effect of LC30 of Bacillus thuringiensisvarkurstaki on the enzymatic activity of non specificesterases ( - and -esterases), alkaline and acid phosphatases and carbohydrate hydrolyzing enzymes (invertase, trehalase and amylase) of the cotton leafwormSpodoptera littoralis (Boisd.) treated as 4th larval instar. It’s clear from our results that the applied concentration induced decrease in the enzyme activities of both  & -esterases at different time intervals post-treatment (6, 12, 24 and 48 hrs.) Alkaline and acid phosphatases activities were significantly decreased (p