Abstract: Pesticidal composition capable of gradual exhalation of the vapors of enhanced synergistic insecticidal activity at ordinary temperature, which comprises a very slightly volatile pesticide, a volatile organophosphorus pesticide and a polymer of vinyl series compound together with the auxiliary additives.Vapor of the volatile insecticide serves to entrain a minor amount of vapor of the very slightly volatile pesticide, while the polymer of the vinyl series compound serves as a carrier base for the pesticides.