We document a decrease in abundance of Cornus florida due to dogwood anthracnose over a ten year period in upland forest of southern Illinois. Ninety seven permanently marked 0.04 ha plots were sampled in 1994 and 2004 in LaRue Pine Hills/Otter Pond Research Natural Area (RNA) in Southern Illinois. Topographic site characteristics measured were slope aspect, position, angle, elevation, terrain shape, landform, and topographical shading indices. Abundance measurements were tree basal area, tree density, sapling density, and seedling density. The abundance of C. florida and co-occurring woody species were quantified in five overstory dominance types including Pinus echinata/Quercus velutina, Quercus velutina, Quercus alba/Quercus species, Quercus rubra, and Mixed Mesophytes. Between 1994 and 2004, the total tree basal area increased by 7.5% while tree density decreased by almost 20%. The overall composition of the tree and seedling layers did not change significantly, but the sapling layer showed a significant change in composition. The greatest change was the decrease in density of Cornus florida by 54% in the tree and seedling layers and 78% in the sapling layer. The greatest decrease in C. florida density was on mesic sites with low slope position and high topographic shading. The decrease in C. florida was likely due to Discula destructiva, the fungal pathogen that causes dogwood anthracnose. Increases in Asimina triloba and Sassafras albidum saplings, and seedlings of Acer rubrum, Liriodendron tulipifera, Ostrya virginiana, and Sassafras albidum along with decreased seedling density of Quercus alba suggests that the loss of C. florida may lead to future shifts in the composition of these forests.