Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko) is a major insect pest of wheat worldwide, especially in the western United States. Cultivars of bread wheat (Triticum aestivum L. em Thell, 2n=6x=42, AABBDD) containing Dn (Diuraphis noxia) resistant genes have begun to be produced and cultivated. However, the development of a new biotype has overcome formerly resistant wheat cultivars. Therefore, it is important to develop understanding of the mechanisms of wheat aphid resistance and to characterize genes involved in plant recognition of and defense response to aphid attack. It is also important to know what aphid gene products are participating in the wheat – aphid interaction on a molecular level. The study of differential gene expression in infested plants and in aphids feeding on those plants provides a wide picture of the metabolic pathways involved in aphid – plant interaction. Mapping and map-based cloning of phenotypically scored single resistance genes is a more a straight forward approach to identify plant genes involved in recognition of the attacker and triggering defense response. Both approaches will be presented and results obtained will be discussed as complementing each other in increasing a general knowledge of mechanisms and eventual cloning of key sequences involved in plant-insect interaction.