Laboratory bioassays on the effect of two plant oils, i.e., cotton seed and safflower oils using different concentrations on E. insulana and P. gossypiella were investigated. Both oils caused insecticidal effects on the two insect pests. Data indicated a great reduction in population growth and weight of the larvae and adults than the control. Cotton seed oil was more effective on both insects than safflower oil. On the other hand, P. gossypiella was more sensitive than E. insulana for both oils. The two plant oils caused a reduction ¡n the total soluble protein and fat contents in the treated insects. Both insects was more susceptible to cotton seed oil than safflower oil.