White-tailed deer (Odocoileus virginianus Zimmerman) have been labeled a keystone herbivore in forests of the midwestern United States, particularly as deer have increased over the past century due to forest fragmentation, reduction of natural predators, reduced hunting, and mild winters. Deer browsing in the Apostle Islands National Lakeshore has had a pronounced effect on formerly large continuous patches of reproductive Canada yew (Taxus canadensis Marshall). In order to compare understory plant communities in 2005 to those at sites sampled in 1958, we resurveyed 32 forest sites on islands that remained free of deer throughout this period, on islands that retained deer, and on islands that gained or lost deer. Multivariate analyses reveal that deer have strong effects on the type of change in the forest understory. Plant communities on sites with long-term deer pressure are becoming increasingly different from those on sites that have never had deer. Four new understory species were detected at these sites, two other species increased by more than 20%, while eight decreased by more than 20%. While grasses and sedges were favored on sites that maintained or gained deer, perennial forbs declined conspicuously on these sites. The recovery of understories on islands where deer were removed suggests that such actions can effectively restore suitable habitat conditions for certain species sensitive to deer herbivory.