Forty old-growth forest stands from the Piedmont Lowland of southeastern Pennsylvania fell into a vegetational gradient with peaks of importance in the order Fraxinus americana, Tsuga canadensis, Acer saccharum, Betula lenta, Quercus prinus, Fagus grandifolia, Quercus alba, Q. velutina, and Acer rubrum (the last three strongly associated with one another). The first three species were important in stands with high soil pH, Ca, Mg, and K, and the other species were associated with lower values of these variables. Fagus importance was significantly associated with high P values. Quercus rubra and Liriodendron tulipifera both occurred broadly across the vegetational and edaphic gradient, but were strongly dissociated from one another. The area, geographically transitional between the Piedmont and Glaciated sections of the former Oak-Chestnut Forest Region, is also vegetationally transitional, for it has a greater importance of non-quercine species then Keever found in the Piedmont to the southwest, but lesser importance of non-quercine species than Buell and co-workers predicted for the (glaciated) New Jersey Piedmont to the northeast.