The mountain pine beetle (MPB), Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae), has had a historically significant impact on the pine forests of southern British Columbia (BC). The current MPB infestation has expanded substantially into the north where it has reached historically unprecedented levels. Terpene-based oleoresins are the main chemical defense employed by pine trees against MPB attack. We investigated the chemical characteristics of the oleoresin of host lodgepole pines, Pinus contorta Douglas, and related it to beetle attack across a geographic range. Phloem samples from numerous trees were sampled in baited, fixed-radius plots at four locations in BC along a north/south transect. There were significant differences in quantities of various terpenes and in MPB attack levels between populations of lodgepole pines in the north compared to those the south. Thus, host tree populations in different geographic regions have differential success in terms of defense against the MPB attack, and the differential success may be due to resin terpene chemistry. Oleoresin toxicity and/or apparency of potential hosts in complex foraging environments could affect differential host-finding and host selection by the insects. Identifying a correlation between oleoresin chemistry and beetle attack can provide a useful tool for refining models that predict the spread of beetles and may provide insight into coevolutionary processes between MPB and one of its hosts.