McEwan, R. W. (Department of Environmental and Plant Biology, Ohio University, Athens, OH 45701), R. D. Paratley (Department of Forestry, University of Kentucky, Lexington, KY 40546), R. N. Muller (Santa Barbara Botanical Garden, Santa Barbara, CA 93105), and C. L. Riccardi (U.S. Forest Service, Pacific Northwest Research Station, Seattle, WA 98103). The vascular flora of Big Everidge Hollow, an old-growth mixed mesophytic forest. J. Torrey Bot. Soc. 132: 618–627. 2005.—Because the goal of natural areas management is often the preservation of biodiversity, documenting botanical species richness is critically important. We conducted a series of botanical surveys in Big Everidge Hollow, a 52 ha watershed containing old-growth forest, on the Cumberland Plateau of eastern Kentucky. We contrasted our findings with a floristic survey that included parts of our study area, conducted approximately 20 years prior. Our research, from 1999 through 2001, yielded 263 species from 176 genera and 82 families, including 19 species that were new records from the site. These new species may have been overlooked in the previous study because of their scarcity or highly cryptic taxonomy, or they may have established in the years between studies. Of the 263 species recorded in our surveys, only one is considered non-native. This remarkable absence of exotic species indicates the high levels of “ecological integrity” inherent the study site and suggests an increasingly vital role for old-growth forests as reference ecosystems.