During summer season, 2014 an experiment was carried out at El-Gemmeiza Agricultural Research Station Gharbia Governorate to evaluate the efficiency and latent effect of chlorpyrifos, tebufenozide, and diflubenzuron on some biological aspects of cotton leafworm Spodoptera littoralis (Boisd.). The efficiency and latent effect proved that these insecticides had high efficiency compared to the control treatment especially for the 4^th instar larvae followed with 5^th instar and 6^th instar ones. Tebufenozide was the most effective compound compared with the other two compounds in suppressing the insect development, while chlorpyrifos recorded the least toxic effect on 6^th instar larvae after 15 days from  treatment. Tebufenozide affected the development  of S. littoralis pupationwhere, zero days of larval feedings treatment recorded zero pupae formation of the 4^th, 5^th and 6^th instar larvae. The highest mortality of pupae was recorded at the 5^th  day after treatments followed by the 10^th  day after treatments and finally at 15^th  day after treatments, for Tebufenozide, diflubenzuron and chlorpyrifos for all instars larvae,respectively.Tebufenozide recorded the highest mortality of pupae. The least moths emergence was recorded with tebufenozide in the 5^th day after treatment with no significant differences with diflubenzuron for the 4^th instar larvae. The moths emergence increased gradually for the three tested compounds from the 4^th to the 5^th and the highest in case of  the 6^th instar larvae. Results showed that all treatments succeeded in reducing the alive instar larvae , high mortality of pupae and less number of moths emergence. Successful results happened to be more promising for the 4^th instar larvae than the 5^th and 6^th instar larvae.