Red oak borer attack height was directly related to red oak size in immature oak stands. Attack density was inversely related to tree size. Borer density within size classes was not significantly different when trees from Pennsylvania stands were compared with trees from Indiana stands. Median attack height was always ≤5 m for trees up to 30.0 cm in diameter at breast height. Almost 75% of the attacks were found in the economically important basal 4-m trunk portion in all size classes of trees.