FMC Corporation initiated a pyrethroid susceptibility monitoring program in 1979 to monitor tobacco budworm, Heliothis virescens, larval susceptibility to permethrin. Cypermethrin was added to the program in 1980. Annual collections of H. virescens have been made in GA, MS, LA, TX, AZ and CA to determine if any changes in susceptibility have occurred. Overall, no consistent or generalized decrease in H. virescens susceptibility has been detected. However, considerable site-to-site and year-to-year variation in susceptibility has been observed with higher LD values typically being followed by lower values in subsequent years.