The present study was carried out toevaluate the effect of spinosad (0.02% W/W SL) against the 2^nd, 4^th and 6^th larval instars of the black cutworm, Agrotis ipsilon (Lepidoptera: Noctuidae) by used various concentrations of spinosad under laboratory and the field conditions in Zefta district, Gharbiya Governorate during season of 2006, spinosad was applied at a rate of 50cm/fedan. Results indicated that a positive relationship existed between larval mortality and concentration except for 6^th larval instar at 25 ml /50g bran, pupation percentage and adult emergence decreased gradually with increasing the concentration except in 10ml/50g bran. Generally, results indicated that abnormal larvae and pupae failed to transform to the next developmental stages during the normal periods as in check. The decrease in the percentage of normal pupation was correlated with increase of concentration of tested compound as well. In the field, cutworm damages in spinosad formulation treated plots were minimized 75.2% for larvae and 78.6% for cut plants. Therefore, spinosad reduced the natural occurrence of cutworm and its damage in cotton field.