Field and Semi-field experiments were carried out in Manshiat-Ganzor in Gharbya governorate during 2009 to study the effect of three biocides used for the control of the cotton leafworm. The treatments included Viroset 4% W.P., Protecto 9.4% W.P. and Prophect 7% W.P. at its half (150gr/F) , recommended (300gr/F) and double dose (600gr/F). The results indicate that the 2^nd instar larvae of Gharbya cotton leafworm fed on the samples of treated leaves for each treatment, only 20, 30 and 20% larval mortality were observed after 3 days to the higher concentration (600gr/F) to viroset, Protecto and Prophect respectively, such larval mortality were increased to 65, 65 and 68% after 13 days to the samples collecting after (zero time). The data indicated that treatment of larvae with the tested biocides drastically reduced the rate of % pupation, % of emergency and increased the mortality and deformation in pupal and adult stages. The treatments also reduced egg production and % hatchability. With regard to hatchability , obtained results indicated that Protecto was the most effective (0% hatchability) followed by Viroset 12.11% and Prophect 15.3% when they were applied at their double dose at zero time of spray. The field experiments showed that Protecto was the most potent biocide in reducing the population of the cotton leafworm larvae after 8 days of application, particularly when this compound used at 600 gr/Feddan. The reduction in larval population after 8 days of treatments with Viroset , Protecto and Prophect at (600gr/F) were 40 , 80 and 77%. The previous results suggest that biocides compounds may be recommended as an effective component of the future IPM programs against Spodoptera littoralis on cotton fields.