Populations of red oak borer, Enaphalodes rufulus (Haldeman), a native wood-boring beetle, seem to be at unprecedented levels that are coinciding with extensive oak mortality occurring in the Ozark Mountains of Arkansas, Oklahoma, and Missouri. To quantify population levels, we developed intensive and extensive sampling methods with respect to the seasonal phenology of active and quiescent stages of the borer’s synchronous 2-yr life cycle. Intensive whole-tree sampling yields data for the entire infested tree bole and provides baseline data for development of less time-consuming sampling methods. Extensive partial-tree sampling uses a nine-sample proportional sampling scheme to estimate densities, which are extrapolated to the whole tree. Data comparison reveals extensive estimates and intensive data are not significantly different, thus verifying extensive sampling as a relatively accurate and acceptable sampling method. Preliminary data from 58 trees confirm epidemic population levels in three areas of the Ozark National Forest in northern Arkansas. Mean number of phloem galleries initiated by current generation larvae on 38 trees was 599 ± 50 (SE) per tree, average number of live red oak borer found in 57 trees was 77 ± 15 per tree, and mean number of previous generation heartwood galleries present in 38 trees was 185 ± 30. Data generated through this research will permit detailed studies of red oak borer biology and mortality, facilitate development of less time-consuming field sampling techniques, and set the stage for further study of factors contributing to the current outbreak and associated tree mortality.