Abstract: Introduction of a parasitoid in new locality is not without risk to indigenous insect`s community, therefore, host range of the parasitoid Lysiphlebus ambiguus associated with Sipha maydis in Pakistan was studied. Eighteen species of aphids mostly associated with graminaceous crops and some others were tested in laboratory to determine their suitability as hosts of L. ambiguus. In 15 minute observation time the parasitoid made significantly higher number of antennal tapping and ovipositional attempts on S. maydis (26.8 and 20.8 respectively) than on other species. Although, it made many tapping and ovipositional attempts on Brevicoryne brassicae (12.2 and 6.0, respectively) it did not complete development in this species. The parasitoid strain existing in Pakistan seems to be highly specific to S. maydis as it completed development only on this species and therefore, poses no risk of parasitization of non target species.