A monitoring programme for Heliothis vireacens first instar larvae was established in 1987 by PEG-US. Eggs were collected from monitoring sites across the cotton belt, from which first instar larvae of the F₁ generation were evaluated for susceptibility to cypermethrin using a foliar residual testing technique. A wide range in the degree of susceptibility to cypermethrin was found across the cotton belt. The least susceptible populations were found at sites located in Texas. Direct comparison of test results with field control effectiveness could not be made, although the general pattern of susceptibility as measured by this test appeared to be consistent with farmer perceptions of pyrethroid performance. The monitoring programme will continue in 1988, making use of the first instar foliar test as a back up to an adult vial test in those areas where high levels of tolerance are recorded.