Hessian fly, Mayetiola destructor, is a destructive pest of wheat that occurs in all of the wheat producing regions of the United States. Thought to be endemic to the southern Caucasus region of Southwest Asia, Hessian fly dispersed west into North Africa and Europe before its introduction into North America in 1776. The pest has since spread across the continent causing substantial economic loss in wheat production through reduction in grain yield. Historical record states that a single introduction into North America occurred; however, to date, the pest has not been studied in reference to its ancestral origins in the Old World to test this hypothesis. Using sequence information from three mitochondrial genes as well as sequence from a nuclear intron, we are beginning to resolve the relationships within and between Hessian fly populations in the United States and between populations in the United States and the Old World. Results test the hypotheses that a single introduction accounts for the genetic variability of Hessian fly in the United States as well as the presumed location of the center of origin in Southwest Asia.