Variation in susceptibility of Arkansas populations of Helicoverpa zea to cypermethrin was studied by topical assays at the University of Arkansas. Samples of colonies collected from the field during 2005 to study susceptibility to Cry1Ac were used as experimental subjects. Standard assay procedures including topical assay of early third instar larvae and use of technical cypermethrin dissolved in acetone were employed. Resulting data were studied by probit analysis. Variability in susceptibility to cypermethrin will be presented in comparison to measured susceptibility to Cry1Ac.