The persistence of several pyrethroid insecticides was determined by mortality of second instar Helicoverpa zea (Boddie) exposed to aged insecticide residues on cotton foliage. Cotton foliage was removed at several postinsecticide treatment intervals and larvae were allowed to feed on the foliage for 72 h in a leaf bioassay. Residual efficacy was longest for applications of Karate 1.0EC, and Karate CSO 0.6EC, followed by Baythroid 2.OEC and Scout X-tra 0.9EC. Residual persistence was shortest for Decis 0. 2EC, Ammo 2. 5EC and Asana XL 0. 66EC. The addition of commercial spray adjuvants did not extend the residual efficacy for applications of Amno 2.5EC or Asana XL 0.66EC.