Fourth instar larvae of Spodoptera littoralis (Boisd) of susceptible, Behera, Dokahlia, Gharbeia, Kafr-El-Sheikh, Sharkeia and Fayoum, Governorates strains  were tested in the laboratory. Tests were carried out using dipping technique with three organophosphate and three carbamate insecticides. Treatments were done before and after spraying programs in the fields of these areas. Summerized data in general reported that the results of LC₅₀ levels after spraying programs were higher than those before spraying. With regard to the activity of esterases of 4^th instar larvae of S. littoralis for each Governorate at Mg/min/larva or Mg/min/gram, it was  clear that the activity increased gradually with increasing the levels of resistance. On the other hand, a positive correlation was obvious between resistance values and esterases activity.