The response by five species of bark beetles to a range of verbenone doses were tested in bioassays using Lindgren funnel traps baited with attractant semiochemicals. The objective was to determine how these bark beetles respond to verbenone, a purported anti-aggregation pheromone of several economically significant bark beetle species. Catches of Dendroctonus ponderosae Hopkins, a species attacking live trees, were unaffected relative to a control trap (no verbenone) at release rates of 0.2 mg/24 h or less, but were significantly reduced at rates of 1.8 mg/24 h or more. Catches of Ips pini (Say) and I. latidens (LeConte), two opportunistic species normally attacking fresh, dead host material, were gradually reduced with increasing verbenone dose. Verbenone did not affect catches of Hylurgops porosus (LeConte) and Hylastes longicollis Swaine, two species normally associated with bark in contact with the ground, where saprophytic microorganisms quickly invade phloem tissue. The effect by verbenone on catches of the five species was consistent with differences in host-age preference. Catches of species requiring relatively fresh host tissue were reduced by verbenone, whereas catches of species accepting aged tissue were unaffected.