Filter papers were impregnated with DDT, methoxychlor, lindane, malathion, and bromophos and the toxicities were compared at 26.7, 15.5, and 10.0°C against the red flour beetle, Tribolium castaneum (Herbst); the confused flour beetle, T. confusum Jacquelin duVal; the sawtoothed grain beetle, Oryzaephilus surinamesis (L.); the merchant grain beetle, O. mercator (Fauvel); and the rust grain beetle, cryptolestes ferrugineus (Stephens). Beetles were exposed on treated filter papers for 24 hours, and mortality was assessed 72 hours after the beetles were returned to flour at the same temperature. Methoxchlor was ineffective against all species except T. castanum . DDT was more toxic to all species at 10.0 and 15.5 than at 26.7°C but was slightly more toxic at 15.5 than at 10.0°C. Lindane was more toxic at 10 than at 15°C to T. castaneum and O. surinamesis , but was more toxic at 15°C than at 10.0°C to O. mercator and C. ferrugineus . Malathion and bromophos showed positive temperature coefficients against all species. Bromophos was much less effective at 15.5 and 10.0 than at 26.7°C against both Tribolium species and O. surinamesis. T. confusum was the most resistant species and C. ferrugineus was the most susceptible to DDT, lindane, malathion, and bromophos. Malathion was the most effective insecticide at all 3 temperatures employed.