Radiant SC12% (Spinetoram) is a new generation of spinosyn group. Effect of this bio-insecticide against larvae of Spodopteralittoralis(Boisd) was studied to evaluate the susceptibility of 2ndand 4thlarval instars in laboratory. The LC50 of radiant was 0.05 and 0.03 ppm. After 24 and 48 hours, respectively for the 2ndlarval instars. Where the LC50 were 6.67 and 2.86 ppm after 24 and 48 hours, respectively for the 4thlarval instars. In the semi-field experiment, recommended doses of radiant exhibited high mortality 100 & 95.7 % after 0 and 1 days, respectively then decreased gradually to reach 58.1 % after 7 days. Also the field experiment showed high mortality 91.4% after 2 days then reduced gradually to reach 83.1% after 8 days. The effect of different concentrations in laboratory and recommended doses in field showed 100% mortality of entire hatched egg masses. Effect of recommended doses of radiant against predators inhabiting cotton field demonstrated that radiant was safe to natural enemies. The effect of LC50 of radiant on the major biochemical component of 4thlarval instars after 24 hours showed that, the amount of total carbohydrates, total proteins, carbohydrate hydrolyzing enzymes (invertase, trehalase and amylase), and acid & alkaline phosphates were significantly decreased. Where theacetylcholinstrase activity was significantly increased. Yasser.Abdelrahman@fsc.bu.edu.eg