Dendroctonus adjunctus is an aggressive bark beetle species that attacks several species of pine throughout its range from southern Utah and Colorado south to Guatemala. A current outbreak of D. adjunctus provided a unique opportunity to study the relationship between this beetle and pine resin chemistry in northern Arizona. We compared the resin composition of trees that had been attacked by D. adjunctus compared with unattacked trees and found significant differences in the composition of the monoterpenes α-pinene, ß-pinene, myrcene and limonene between attacked and unattacked trees. Attacked trees contained significantly higher percentages of α-pinene, myrcene, and limonene, but lower levels of ß-pinene when compared to unattacked trees. Although it is unknown whether D. adjunctus prefers or is repelled by trees with specific monoterpene content, our results suggest that D. adjunctus may use specific chemical cues in host tree selection.