Reduced neuronal sensitivity (= target site resistance) to the pyrethroid, allethrin was detected in tobacco budworms collected from the Red River (RR) and Macon Ridge (MRS) field stations in northern Louisiana during the 1995 cotton season. Expression of this resistance mechanism was similar between male and female larvae but differed between sexes in adults from the MRS location. No differences in expression were measured between male and female adults collected at the RR site. In addition, patterns of expression were compared between larvae and adults collected during the early- and late-season at the MRS location. Although expression of target site resistance in larvae was greater in the late- than early-season collection, frequencies of expression in adults were similar for the two collections. Finally, expression of this mechanism was compared between adults that were collected at the same location from either pheromone traps or with sweep nets. Differences in frequency of expression of target site resistance were found between pheromone-trapped and sweep-netted adults from MRS but not RR, suggesting potential differences in toxicological attributes of insects collected by these two methods. The significance of these findings with respect to the utility of the adult vial test as a monitoring tool is discussed.