The toxicity of azinphosmethyl, parathion, monocrotophos, chloropyrifos, phosfolan, methomyl, and endosulfan to adultChenolus inanitus(L.), a parasitoid ofSpodoptera littoralis(Boisduval), was studied. The insecticides were sprayed on cotton plants in the field. Treated leaves, at different intervals after the treatments, were cut and checked in the laboratory for their effects on the mortality ofC. inanitus.The effective time of various insecticides from the day of spraying the cotton field until the decrease in death of the female parasitoids from 100 to 50% was found to be (in days): parathion—45; azinphosmethyl—42; phosfolan—37; monocrotophos—28.5; chlorophyrifos—22; methomyl—19; and endosulfan—14.5.The persistence for long periods of residues on the cotton plants hinders the possibility of any progress in integrated control programs for cotton insect pests.