The invasive emerald ash borer (Agrilus planipennis Fairmaire) (Coleoptera: Buprestidae) is an Asian beetle that feeds on ash (Fraxinus spp.) trees. Emerald ash borer was discovered in southeastern Michigan in 2002 and has subsequently been found to be responsible for the death or decline of several million ash trees. We examined the historical dispersal patterns and spread of emerald ash borer over a geographic area encompassing the known core infestation in southeastern Michigan. Increment core samples were collected from emerald ash borer-killed ash trees at regular intervals throughout the region. The temporal and spatial dynamics of emerald ash borer were reconstructed using dendrochronological analyses.