Red oak borer, Enaphalodes rufulus (Haldeman), is a native insect that develops primarily in living red oaks from Minnesota and Texas to the Atlantic coast. Populations are usually at low levels and it has never been reported as a significant mortality agent. In oak-hickory forests of the Ozark Mountains of Arkansas, populations have significantly increased since the late 1990’s. The two-year life cycle of this cryptic species is complicated by synchronous adult emergence only in odd-numbered years. Determining the best sampling strategy to accurately assess red oak borer populations within trees and stands, has been a primary lab research objective and has led to the development of a series of sampling procedures. Intensive dissection and mapping of all physical evidence of red oak borer yields data on current beetle life stages and survivorship and on previous generations infesting the tree and provides data for development of subsequent sampling procedures. Data derived from 24 intensively sampled trees revealed that extensive sampling of nine stratified samples from each tree could accurately estimate whole-tree populations. Further optimization of extensive sampling was investigated in an effort to determine the optimal number of samples in regard to time, effort and statistical reliability. Data from 69 intensively and extensively sampled trees validated a rapid estimation procedure used for non-destructive field population counts in stands experiencing outbreak populations. These sampling methods should prove valuable in future efforts in monitoring red oak borer populations and could guide efforts in investigating populations of other stem-boring insect species.