Since at least 1999 oak-hickory forests of the Arkansas Ozarks have experienced extensive oak mortality due in part to a native wood-boring beetle, the red oak borer Enaphalodes rufulus (Haldeman) (Coleoptera: Cerambycidae) which has an unusual two-year lifecycle. This unexplained outbreak has caused severe economic, ecological, and public safety concerns. Historically, red oak borer has been found at relatively low population density, but preliminary infestation estimates in 2001 and 2003 reported significantly higher densities. During 2005 red oak borer population parameters were quantified from seven ridge tops across the Ozark National Forest. Objectives were: 1) Compare population density estimates from 2001 and 2003 to the 2005 generation; 2) Determine if oak-hickory stands on ridge tops across Ozark National Forest exhibit similar red oak borer abundance; 3) Estimate overall larval mortality and compare with 2003; 4) Compare red oak borer density and mortality among three classes of tree vigor. At each of the seven sites, nine red oak trees (Quercus rubra L.) were categorized into one of three classes using a rapid estimation procedure designed to indicate tree health and red oak borer infestation history. Trees were felled, cut into 0.5 m sections, split on site using hydraulic log splitters, and number of red oak borer recorded. Seven sample logs proportionally selected from each tree based on height of infested bole were removed and returned to the laboratory for dissection and quantification of current generation galleries. This information was used to estimate larval mortality.