Technical Abstract: Foreign pest insects present an ongoing challenge to the safety of U.S. agriculture. One such invasive threat to the U.S. cotton industry is Oxycarenus hyalinipennis (Costa) or the cotton seed bug. Populations are found throughout most of the world except for North America, and the southeastern U.S. is believed to provide a favorable environment for its establishment. A major component in efforts to control the spread of invasive pests is the rapid and accurate identification of intercepted specimens. Unfortunately, O. hyalinipennis belongs to a taxon that is not characterized extensively and where assignment of species identity by simple morphological keys often is problematic. An alternative strategy takes advantage of advances in molecular technology that allow the rapid analysis of DNA sequence data from even small amounts of tissue. “DNA barcoding” uses DNA sequence comparisons of conserved mitochondrial gene segments to estimate phylogenetic relationships between organisms. While controversial, the method has shown promise for assigning species identity to unknown specimens. In this study, we assessed the potential of DNA barcoding to identify the cotton seed bug in field collected specimens and demonstrated that despite some limitations, this molecular method would significantly facilitate current efforts to monitor for this important pest.technology that allow the rapid analysis of DNA sequence data from even small amounts of tissue. “DNA barcoding” uses DNA sequence comparisons of conserved mitochondrial gene segments to estimate phylogenetic relationships between organisms. While controversial, the method has shown promise for assigning species identity to unknown specimens. In this study,we assessed the potential of DNA barcoding to identify the cotton seed bug in field collected specimens and demonstrated that despite some limitations, this molecular method would significantly facilitate current efforts to monitor for this important pest.