Technical Abstract: We used a genomics approach to identify some of the genetic basis of D. citri biology, identifying in particular genes associated with feeding, reproduction, pathology, and insecticide resistance. The Asian citrus psyllid (AsCP), Diaphorina citri (Hemiptera: Psyllidae), is a highly competent vector of the phloem-inhabiting bacterium C. Liberibacter asiaticus, the agent of huanglongbing (also referred to as citrus greening disease). We created and analyzed two expressed sequence tag, EST, libraries made from adult D. citri, one field collected from citrus trees and another from psyllids on citrus in culture. Comparison of these gene sets identified genes which respond to environmental stresses. We produced two data sets of ESTs from adult AsCP. Of the 5,906 ESTs generated from single-pass 5' end sequencing, 4,595 ESTs were quality and averaged a length of 553 bases. Contig alignment resulted in 636 total sequences after assembly (544 contigs plus 92 singlets). These D. citri gene expression data sets advances current research efforts in the identification of genes and physiological processes of psyllids, however, a much greater knowledge of psyllid genomics is still needed. A full genomics approach will rapidly advance the understanding of the genetic basis of D. citri biology and the endosymbiotic bacteria. Development of these genetic products will set the foundation for functional genomic studies needed for the development of emerging management strategies aimed at reducing psyllids and the spread of HLB, citrus greening disease. These data have been submitted into GenBank, NCBI, database.