Summary The effect of sublethal concentrations 0.00141%(LC20), 0.00251%(LC30) and 0.00336% (LC40) of a dispersible concentrated formulation of the insect growth regulator flufenoxuron (Cascade®), on larval growth and development, adult reproductive potential and egg hatchability of the red flour beetle, Tribolium castaneum, was investigated. When neonates were subjected to sublethal concentrations of flufenoxuron in artificial diet for 24 h, there were dose-dependent effects on larval weight, percent pupation and percent adult emergence, as well as time taken for adult emergence. A small proportion of larval-pupal as well as pupal-adult intermediates were observed at all concentrations. Adults emerging from the LC20 and LC30 concentrations laid mostly non-viable eggs, and the few larvae which emerged from viable eggs died at the first instar stage. At the LC40 concentration, all the adults that emerged were deformed and subsequently died. Flufenoxuron exhibited transovarial ovicidal activity resulting in the production of non-Viable eggs upon exposure of adults of different ages (2 days old, 3 days old and 4 days old) to treated diet. It was observed that in 2-day-old adults, fecundity decreased with an increased concentration. In the case of 3-day-old adults, there was no difference in fecundity with respect to the concentrations tested, although it was significantly less than the control. In the case of 4-day-old adults there was a drastic reduction in fecundity at LC40 and the eggs laid were abnormal at all concentrations. Topical application of sublethal concentrations of flufenoxuron to adults of either sex reduced the fecundity in a dose-dependent manner. Furthermore, the fecundity was reduced drastically in pairs where both the sexes were treated as compared to the pairs where only one sex was treated. Eggs showed a decrease in hatching percentage with increasing concentrations of flufenoxuron mixed with diet to which the eggs were exposed.