The lethal and sublethal effects of five insecticides from different groups namely: chlorfluazuron, emamectin benzoate, pyrethrins and Bacillus thuringiensis subsp. kurstaki compared to one of the most known organophosphorous compound (chlorpyrifos)as a chemical insecticide, were evaluated on the 2^nd instar larvae of a laboratory strain of cotton leafworm, Spodoptera littoralis (Boisd.). The toxicity effect indicated that emamectin benzoate proved to be the most effective compound among all tested insecticides. Some biological aspects were also investigated to show the latent effects of the tested compounds, such as; duration periods of larval and pupal stages, mortality percentage in pupal stage, pupation percentage, weight of pupae, percentage of adult's emergence, longevity of adult stage (male & female), sex ratio, female fecundity of eggs, incubation period and percentage of egg's hatching revealed that all compounds varied in their influences on biological aspects, and these biological aspects could have relation with toxicity of insecticides against S. littoralis larvae.