In order to investigate the comparative effectiveness of some  insecticides including pyrethroids (Alpha cypermethrin and Fenvalerate) , organophosphates (Chlorpyriofos, Cyanophos and Profenofos ) and carbamates (Methomyl ) bioassay experiments were performed on the 4^th larval instars of Spodoptera littoralis. Surveys or monitoring level of toxicity in some governorates of Egypt (Beheira, kalubia, Dakahlia, Fayum, Beni suef) and laboratory strains, were determined . According to LC₅₀ and LC₉₀ values the data revealed that pesticides were  highly effective on laboratory strains The other strains or governorates populations tested with insecticides were less affected  and behaved  differently according to the strain location . Resistance ratios ,  analyzed protein of all governorate population tested by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and electrophoretic patterns of esterase isozyme during the larval stage were determined.