Ethyl alcohol, acetone, and petroleum ether extracts of three plant species belonging to three different botanical families [Strychnos nux-vomica (Loganiaceae), Euphorbia lathyrus (Euphorbiaceae), and Datura stramonium (Solanaceae)], a chemical insecti¬cide; profenofos and their combinations were tested against second and fourth instars of Spodoptera littoralis under lab conditions. Results revealed that the ethanol extract of S nux-vomica was the most effective among all plant extracts, where the corrected mortality% were 92, 81, 58, and 27% to 2nd instar and 89, 74, 34, and II % to 4th instar at concentrations 0.5, 0.25, 0.125, and 0.0625%, respectively. Calculated LC su's were 0.11, 0.22, and 0.34% to 2nd instar and 017, 0.37, and 0.52% to 4th instar for ethanol, petroleum ether, and acetone extracts, respectively. Acetone extracts of all plants were of lower effect. The chemical insecticide profenofos displayed higher effi¬cacy than plant extracts (LCsu = 0002 and 0.003% for S littoralis 2nd and 4th larval instars, respectively). The co-toxicity factor reached 76 and 60 when mixing S nux¬vomica + profenofos and D. stramonlum + profenofos at ratio I: I against S littoralis 2nd instar larvae, thus indicating a potentiating effect. While treatment of the 4th instar larvae by the same mixtures resulted in a co-toxicity factor below 20 at all mix¬ing ratios indicating, only, an additive effect against this instar