Cathedral State Park (CSP) is a 54-ha, old-growth, eastern hemlock-hardwood forest located in the central Appalachian Mountains of West Virginia. Hemlock woolly adelgid (HWA) (Adelges tsugae Annand) is an exotic insect that currently threatens eastern hemlock (Tsuga canadensis (L.) Carr.) in its native range, and was found in CSP in 2002. In 2006, field plots established in 2000 were re-measured to assess adelgid-induced changes to forest structure and species composition. The herbaceous plant community was also measured during the 2006 growing season to describe how the ground flora has changed since it was originally surveyed in 1965. In addition, characteristics of snags and downed dead wood in CSP were compared to published data on 25 old-growth hemlock-hardwood stands in the eastern United States. From 2000 to 2006, little HWA-induced change occurred in CSP. Density and basal area of overstory hemlock did not change, while snag density and basal area decreased over time. However, more than 10% of measured overstory hemlock trees were infested with HWA, with plot infestations ranging from 0 to 93% of stems. CSP had 1.5 times the volume of downed dead logs compared to other old-growth hemlock-hardwood stands. This study serves as a reference of forest structure and species composition in CSP prior to HWA-induced mortality.