An insecticidal composition which contains a combination A of O,O-dimethyl S-[1,2-bis-(ethoxycarbonyl)-ethyl] dithiophosphate with at least one of the insecticides defined under (a) and (a') below:(a) O,O-dimethyl S-(4-aza-6-chloro-2-oxo-benzoxazol-3-yl)-methyl thiophosphate, and(a') an ortho-substituted phenyl N-methylcarbamate having the following formula: ##STR1## in which R is an alkyl radical containing 1 to 5 carbon atoms, a propargyloxy radical, a dialkoxymethyl radical in which the alkoxy group contains 1 to 4 carbon atoms, a dioxolanyl radical or a dioxanyl radical, these two latter radicals being unsubstituted or substituted by 1 or 2 methyl groups, and R' is a hydrogen atom, or R and R', together with the two carbon atoms of the benzene ring to which they are attached, form a thiophene ring, a dioxolane ring or dihydrofurane ring, these rings being unsubstituted or substituted by one or two methyl groups.