Aphids (Hemiptera: Aphididae) are phytophagous insects that are importantagricultural pests. The enormous negative economic impacts caused by aphids worldwide arewell known, and are mostly due to their high multiplication rate and the transmission ofphytopathogenic viruses. Aphid management strategies mainly involve chemical treatmentswhich are pollutants and are increasingly inefficient, since aphids have developed multipleinsecticide-resistant mechanisms. Among the most economically important species is thegreen peach aphid Myzuspersicae Sulzer (Aphididae: Macrosiphini), which is able to colonizea wide range of host plants belonging to many different families, and transmits numerous plantviruses. Because of its large prevalence, M. persicae has been the target of massive insecticidetreatments; consequently, it has evolved several insecticide-resistant mechanisms. In thiswork, a collection of expressed genes from M. persicae is presented in order to identify putativegenes involved in xenobiotic detoxification. After cDNA cloning and sequencing, 959expressed sequence tags (EST) were annotated. Most sequences matched known genescorresponded to metabolism proteins (26%), ribosomal proteins (23%) and structural proteins(8%). Among them, several sequences corresponded to proteins putatively involved in sensing,degradation or detoxification of plant xenobiotic products.