An impact survey to determine extent and distribution of root disease centers was completed for the Nezperce National Forest, Idaho, in 1980. Lowlevel color infrared photography was used to delineate root disease centers within National Forest inventory subcompartments. Suspected root disease centers were ground checked to determine associated fungi and insects and verify accuracy of photointerpretation. More than 3,800 hectares (about 1.0 percent) of commercial forest land were occupied by large root disease centers. Most root disease occurred in well-stocked, pole to small sawtimber stands and medium-stocked, two-storied stands. The major root pathogen associated with disease centers was Armillaria mellea. Phellinus weirii and Phaeolus schweinitzii were found less frequently. Major bark 1 beetle associates included Dendroctonus ponderosae on lodgepole pine, D. pseudotsugae on Douglas-fir, Dryocoetes confusus on subalpine fir, and Scolytus ventralis on grand fir.