A study was carried out to determine the comparative efficacy of five new insecticides viz., diafenthiuron (polo 50%SC), thiamethoxam (actara 25%WG), acetamiprid (diamond 20%SP), imidacloprid (confider 20%SL) and thiacloprid (calypso 24% OD) at field recommended doses against whitefly, Bemisia!abaci (Genn.) on cotton variety Bt-121 grown at farmer field on 25th May, 2009 at Chak No. 253/R.B, Faisalabad. Insecticides sprayed when population of whitefly reached to economic threshold level (ETL) i.e., 4-5/leaf. The data regarding mean number of whitefly per leaf was taken and converted in to mean percentage mortality to find out differences among the treatments. The results of present study showed that lmidacloprid, diafenthiuron, acetamiprid and thiamethoxam were most effective insecticides against whitefly up to seven days after application. While, lmidacloprid and diafenthiuron gave maximum mortality during first spray (89.52 and 85.80%) and second spray (91.67 and 87.51%) after 72 h of application.