Ponderosa and Jeffrey pine sapwood samples and freshly cut stumps from trees with different amounts of oxidant injury were inoculated with Fomes annosus. With stumps, percentage of surface cross-section area infected and extent of vertical colonization were determined 1 mo and 6-10 mos after inoculation, respectively. Increase in surface area infection with increased oxidant injury, expressed as upper-crown needle retention was statistically significant for ponderosa pine (P=0.01), but was not for Jeffrey pine. Also, the rate of vertical colonization was greater in stumps from severely oxidant-injured trees than in those from slightly injured trees. The relationship between injury and colonization was significant for Jeffrey pine (P=0.05) and for ponderosa pine at one site (P=0.03), but nonsignificant (P=0.18) for ponderosa pine at a second site. Increased susceptibility of stumps to F. annosus appeared to be associated with decreased oleoresin exudation and decreased colonization by other fungi (especially Trichoderma spp. and blue stain fungi). (Copyright (c) 1980 The American Phytopathological Society.)