Laboratory strain-R of Tribolium castaneum, resistant to lindane and multi-resistant strain-L, having developed resistance to lindane and malathion under field conditions, were compared with the standard susceptible strain-S for the nature of resistance to different groups of insecticides. Lindane resistance in both the strains extended to aldrin, dieldrin, endrin and heptachlor. Unlike laboratory strain-R, resistance did not extend to endosulfan in the field strain-L. Both the strains were found susceptible to p, p′-DDT, methoxychlor and allethrin. Also, lindane resistance did not extend to organophosphorous insecticides, viz., malathion, fenitrothion and dichlorovos. Lindane resistance extended to carbaryl and carbofuran, and only slightly to propoxur in the laboratory strain-R, whereas field strain-L remained susceptible to this group of insecticides. Synergist piperonyl-butoxide was found to overcome cross-resistance to endosulfan and propoxur, but to carbaryl in the lindane resistant strain-R. It is, therefore, indicated that one of the three mechanisms responsible for lindane resistance in the laboratory strain of T. castaneum, was stable in the field strain. Thus, the other two mechanisms showing cross-resistance to endosulfan and carbamates were unstable.