Peanuts treated with 20.9, 36.4 or 52.2 ppm pirimiphos-methyl to asses effectiveness of the insecticide were held in open-top, 141. 6-liter, cylindrical bins for 12 mo. in a warehouse infested with 10 species of stored-product insects. Peanuts treated at 52.2 ppm malathion were the standard. Pirimiphos-methyl was as effective or more effective than the standard in reducing the number of insects. Also, peanuts treated with pirimiphos-methyl had fewer insect-damaged kernals than those treated with malathion. Red flour beetles, Tribolium castaneum (Herbst), and almond moths, Cadra cautella (Walker), were the predominant species found. Residues of pirimiphos-methyl decreased gradually at a rate ca. 33per thousand less than malathion during the 12-mo period.