Reproduction in mountain pine beetle (Dendroctonus ponderosae Hopkins) is contingent upon successful search for and attack of a suitable host tree (Pinus spp., especially lodgepole pine, Pinus contorta var. latifolia). This search for a host involves both visual and olfactory cues, including beetle-produced pheromones involved in ‘mass attack' which is required to overcome host defences. Beetles can be choosy while making host selection decisions, discriminating based on host size, quality, and defensive capability, as well as conspecific (attack) densities. However, the extent of their ‘choosiness' appears to be modulated by individual energy (i.e. lipid) reserves. A stochastic dynamic programming model of individual beetle host-selection, based on an individual’s energy state, is presented. Field data are incorporated into model parameterization and the effects of host availability, quality, and vigour on individual’s decisions and their subsequent implications for attack dynamics of the population are discussed.