A monitoring system was developed to measure the occurrence of resistance to synthetic pyrethroid insecticides in the tobacco budworm (TBW). Monitoring was conducted by Extension Service entomologists in more than a dozen areas of Texas. To monitor for resistance to cypermethrin, pheromone-trapped males were placed in vials treated with cypermethrin at doses from about the LC98 for a susceptible strain to 10 times that dose and the responses determined. Early season results (April-May) indicated near universal susceptibility in field collected TBW. In June and early July a few insects demonstrated resistance. By late July-early August most TBW tested were resistant in the Uvalde and Brazos Valley areas. Resistance occurred in several other areas of the state at a lower frequency. Late in the season monitoring was extended to Arkansas. Louisiana, Mississippi and California. Evidence was obtained for pyrethroid resistance in the TBW in each state. Based on these results we conclude resistance to synthetic pyrethroids is present in the TBW in most of the U.S. cotton belt.