Field trials were conducted at El-Gharbia governorate to determine the insecticidal activities of chlorpyrifos-methyl, profenofos and methomyl on tomato plants against the cotton leaf-worm (Spodotera littoralis). Data showed the high initial mortality (100, 100 and 100%) against the second and the fourth instars larvae with reasonable persistence. The residues of these insecticides on fruits of the sprayed and contaminated tomato plants were determined by GLC and HPLC, with recoveries of 100, 100 and 94.58%, respectively. The initial deposits of chlorpyrifos-methyl, profenofos and methomyl were 2.10, 2.58 and 20.11ppm, while decreased to 0.19, 1.41 and 0.33ppm after 3,1 and 13 days from spraying, respectively, such residue levels are below the maximum residue level (MRL). The estimated half-life values (t0.5) were 0.4898, 1.026 and 1.1867 days for the same insecticides, respectively