Approximately 42% of Mississippi's cotton crop was planted to transgenic Bt-varieties in 1996, the first year of commercial availability of this technology. Despite unusually low populations of tobacco budworm, Heliothis virescens, the primary target pest of this control tool, overall performance of Bt-cotton was positive. Overall yields were slightly better than conventional varieties and insect control costs were similar. Some Bt-cotton required supplemental foliar treatments to control unusually high populations of bollworms, Helicoverpa zea. However, based on an end of season survey, the number of bollworm/budworm treatments required per field of Bt-cotton (0.33 treatments/field) was considerably less than for conventional cotton (3.05 treatments/field).