Studies with Aedes aegypti were undertaken to determine if an alien genotype can be (1) incorporated into a natural population and (2) maintained for several generations on its own without any subsequent introductions. Such information is an essential prerequisite for successful application of any genetic control method. Data from a walk-in, field population cage and from field releases of a genetic marker and a chromosomal translocation have demonstrated both genetic incorporation and persistence for at least three successive generations. This is the first demonstration of its type with any vector species.