Using a dendrochronological scar dating technique, we examined historical fluctuations in red oak borer numbers in northern red oak from four study sites located within the Ozark and Ouachita National Forests. Recently, these forests have experienced a red oak borer outbreak of a greater magnitude than previously reported in the literature. We examined patterns of red oak borer activity throughout time in trees severely infested during the recent outbreak to determine important factors associated with this epidemic. Study trees were first colonized by red oak borer in the 1930s, and scar numbers remain low until the 1980s, when numbers reached 66 times their previous levels during peak outbreak years. Peak outbreak years were 1996 and 2002 for the Ouachitas and Ozarks, respectively. Red oak borer activity appears to be closely associated with tree growth, as reductions in ring width occur just prior to increases in scar numbers. A significant decline in ring width occurs during the red oak borer outbreak. Scar numbers increase following drought periods when red oak borer is at endemic levels in the Ouachitas. This pattern does not exist at any study sites when at epidemic levels, suggesting that while drought may be important when numbers are low, it does not appear to be directly associated with the recent outbreak.