The present situation and objectives of mass rearing insects are reviewed under the aspect of behavior. The highest degree of “typical” behavior is required in those species that have to compete with their natural counterparts in the field. Selection pressure and conditioning during the process of mass rearing might alter the behavior of the organisms produced under artificial conditions and cause failures of field-releases. Problems that warrant more considerations are displacement failure to reach natural counterparts and the possibility of the evolution of new pest species. A sequence of actions is suggested for establishing a quality control program that elucidates the behavioral status of laboratory-reared strains.