The toxicity of thiamethoxam/chlorantraniliprole, novaluron, chlorpyrifos-methyl and methomyl applied at recommended rates was studied against the cotton leafworm Spodoptera littoralis on tomato plants, during the summer seasons of 2010 and 2011 at Etay El-baroud Agricultural Research Station, El-Beheira Governorate. The % mortalities average (initial kill) caused by thiamethoxam/chlorantraniliprole, novaluron,  chlorpyrifos-methyl and methomyl were 83.8, 84.8, 91.2 and 87.4%, respectively against 2^nd instar of Spodoptera larvae, and were 82.5, 77.2, 89.9 and 87.4%, respectively against 4^th  instar of Spodoptera larvae, while %mortality average (residual toxicity) were 86.0, 70.5, 71.9 and 62.6%, respectively against 2^nd instar of Spodoptera larvae, and were 71.7, 61.9, 67.6 and 56.9%, respectively against 4^th  instar of Spodoptera larvae. From these data it is clear that the two novel tested insecticides have a potent insecticidal activity against both 2^nd and 4^th   instars S. littoralis larvae. Results revealed that tested insecticides were more effective on second instar than forth instar and showed significant differences between tested insecticides.