The effect of different groups of chemical additives: surfactants (polyethylene glycol 600 dilaurate, polyethylene glycol 600 monolaurate and Sisi 6), sticking agents (Glue and Arabic gum), thickening agents (poly acryl amid and hydroxy methyl celelluse) and acidifying agents (citric acid, oxalic acid, sulphonic acid and tartaric acid) on physico-chemical properties, efficiency and persistence of Curacron and Superalpha were studied against 4^th instar larvae of the cotton leafworm S. littoralis (Boisd.). The surface tension and pH value of insecticides decreased whereas the viscosity and conductivity increased as a result of mixing with the adjuvants. Such change in physical properties of insecticides led to increase in their retention and insecticidal efficiency. Generally the effect of tested additives on physico-chemical properties of Curacron and superalpha was as follow:  Sulphonic acid gave the highest decrease in surface tension. Polyacryl amid and hydroxyl methyl celelluse (HMC) recorded the highest increase in viscosity. Oxalic acid gave highest increase in electrical conductivity and lowest decrease in pH value of tested insecticides. Sisi 6 increased effectiveness of 3/4 recommended rate of Curacron to be higher than full recommended rate against S. littoralis (Boisd.), but polyacryl amid increased the persistence of Super alpha to be higher than 3/4 recommended rate but less than complete rate.