Technical Abstract: The following technical abstract refers to the (5th of 6) invited oral presentations given by Dr. Skoda at the APHIS-ARS-Mexico US Commission for the kjEradication of Screwworm Meeting, March 2000. Screwworms, devastating pests of all warm-blooded animals, were successfully eradicated from the US, Mexico, and most of Central America through an eradication program using the sterile insect technique(SIT). The SIT relies on mass-reared, sterile males that are released into the environment and mate with fertile females that then deposit non-viable egg-masses. Currently, there is no way to separate males from females during mass rearing of screwworms. A genetic sexing strain, in which females are selectively eliminated early during development, would improve the efficiency of SIT. At the Midwest Livestock Insects Research Unit, research has been ongoing to develop an insecticide resistant strain of screwworms. Once developed, the gene responsible for insecticide resistance would be moved to the Y-chromosome so that treatment with a low dose of insecticide early in mass rearing would result in only males surviving. After ten generations of selection pressure, insecticide tolerance in the screwworm strain has been elevated three fold. We will also explore the use of heat shock in the process of developing a genetic sexing strain. Previous success in the Mediterranean Fruit Fly Program indicates that the time needed to develop a genetic sexing strain of screwworm may approach ten years.