Insect growth regulating properties of petroleum ether extracts of 10 indigenous plants were tested against Culex pipiens fatigans (Wied) and Musca domestica nebulo (Fabr) by continuous exposure and topical application methods. Out of the 10 plants, Acorus calamus and Azadirachta indica demonstrated insect growth regulatory (IGR) activity against C. p. fatigans and also against M. d. nebulo. There was IGR activity, but this was observed only when these extracts were used in higher concentration.