Genetic improvement of insects has generated only a moderate amount of discussion in recent years because entomologists believe that little of practical importance has been achieved. Meanwhile, the problem of maintaining the genetic quality of laboratoryreared insects has become prominent.However, some insects have been improved genetically. Domesticated and semidomesticated insects such as the honey bee and the silkworm have been improved in many ways through selection and hybridization. Some parasites have also undergone selection to improve insectary production or field effectiveness, or both. “Improved” insects for laboratory tests may be obtained by hybridizing 2 inbred lines, which often yields a vigorous, uniformly variable insect.Parasites, or any insect that must survive and reproduce in a natural environment, present particularly difficult problems for a genetic improvement program. Desirable attributes to be selected must be clearly definable, which is often quite difficult given our current lack of knowledge of the behavior of parasites under natural conditions. Adequate genetic variability must be provided for so that selection can operate, and adequate selection procedures are important. Finally, maintaining the integrity of the improved insects may or may not be important, depending upon how the parasites are used.Heterosis has been largely ignored in programs for the genetic improvement of parasites, but some data suggest that heterosis could increase the effectiveness of inoculative and inundative releases of parasites or predators. There is still not enough experimental evidence to support judgments about the cost/benefit ratios of genetic improvement, however. Future studies must include field evaluation to demonstrate the value of such improvement programs.