ABSTRACTMorphology of basidiospores and pilocystidia of specimens ofGanoderma colossum, G. zonatum, G. oregonense, andG. meredithaewas compared. Structure of basidiospores was similar in all species, but basidiospores of some species differed in length, width, spore index, and shape and distribution of inter-wall pillars. Basidiospores ofG. zonatumwere cylindrical, while those of the other species were ovate with truncated apex. Basidiospores ofGanoderma colossumhad angular inter-wall pillars while those of the remaining species were cylindrical. Pilocystidia were davate and unbranched for most species, but those ofG. zonatumwere highly branched or lobed. Pilocystidia ofG. colossumwere thin-walled, negative to weakly amyloid. Those ofG. zonatumwere thick-walled, negative to weakly amyloid, while those of the remaining species studied were thick-walled and strongly amyloid. Host relationships are reviewed and known geographical distributions are indicated for each of the species studied.