During summer season 2011 an experiment was carried out at El  Gemmeiza Agricultural Research Station, Gharbia Governorate to evaluate the efficiency and latent effect of six IGR compounds on 2^nd  and 4^th  larval instars of cotton leafworm Spodoptera littoralis (Boisd.). The tested compounds were: Caprice, Kingbo, Leveuron, Steward, Virtu and Dimeuron. The efficiency and residual effect proved that these products induced high efficacy in this respect . The Leveuron compound was the most effective compared with other compounds, while Steward recorded the least toxic product on both 2^nd  and 4^th  instars as the initial effect. Reduction percent at end of larval stage of the 2nd and 4th instar larvae ranged between 100% and 50% for Leveuron and Steward; respectively. Also, results obtained indicated that Caprice, Kingbo and Dimeuron compounds induced high level of reductions of insect population. The residual effect of the tested compounds after 7, 14 and 21 days proved that Leveuron treatment had the highest efficacy against cotton leafworm S. littoralis which ranged between 100% to 88%, while Steward treatment gave the lowest one in both larval stages. The biological aspects of These compounds showed that all treatments succeeded in reducing the weights, the instar period of larvae and the leave consumption for the 4th instar larvae.