The LC values for malathion-resistant (PAK) and organo- 50 phosphate-susceptible (FSS-II) strains of red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) adult beetles were determined through filter paper impregnated method against azadirachtin (Nimbokil 60 EC) and polychlorinated petroleum hydrocarbon (Tenekil 100 EC). The LC values of these insecticides were worked out as 12830 and 50 9331 ppm for azadirachtin and 5148 and 4047 ppm for Tenekil 100 EC against PAK and FSS-II strains, respectively. The results revealed that polychlorinated petroleum hydrocarbon was more toxic than the azadirachtin. Furthermore, both the insecticides were equally toxic to the adult beetles of T. castaneum as the difference was non-significant because of overlapping 95% FLs to LC.