Norvell, LL (Pacific Northwest Mycology Service, Portland, OR, 97229-1309, USA) & RL Exeter, RL (USDI Bureau of Land Management, District Office, Salem, OR 97306, USA). Ectomycorrhizal epigeous basidiomycete diversity in Oregon Coast Range Pseudotsuga menziesii forests—preliminary observations. Memoirs of The New York Botanical Garden 89: 159–189. 2004.––The authors present four years of data obtained from concurrent studies researching species richness of western North American Douglas-fir ectomycorrhizal epigeous basidiomycete (EEB) communities in two different Oregon Coast Range forests. Also targeted are 40 nonectomycorrhizal basidiomycetes (NEB) flagged in the US government’s Northwest Forest Plan. A BLM Reserve Forest near Pedee (Polk County) is the site for a 5-year chronosequence study sampling EEB fruitbodies from 25-, 55-, and 150-year old stands. The 56-year old Green Peak (Benton County) BLM Research Forest hosts a 6-year BLM Density Management companion study that explores the impact of timber removal on the same target fungal community by monitoring adjacent plots that in 1999 were regeneration cut (leaving no residual trees/ha), thinned (leaving approximately 300, 200, or 100 residual trees/ha), or left untreated as a control (with~ 420 trees/ha). In 1998, permanent strip transects (2 per stand or plot= 400 m2) were established at both sites. During fall and spring from 1998 to 2002, chronosequence and density transects were inventoried a total of 20 and 18 times respectively; 253 (chronosequence) and 203 (density) EEB species were identified from a combined total of 4,123 collections and 531 (309 EEB) species. Agaricales comprised~ 69%, Russulales~ 19%, Phallales~ 7%, Boletales~ 3%, and Cantharellales~ 2% of the overall EEB species. Cortinariaceae comprised~ 85% of the Agaricales; Cortinarius (95 spp), Inocybe (62 spp), and Russula (50 spp) were the most species-rich genera. Preliminary analyses show that while all Douglas-fir age classes exhibit high species richness (130-164 EEB species per stand), there are differences between stand age and generic representation, in part correlated to the presence of western hemlock. After timber removal, density study stand species richness post/pre-treatment ratios were significantly depressed in the two most heavily thinned stands, but light to moderate forest thinning did not appear to have much effect on EEB species diversity. The unusually high number of species identified supports earlier hypotheses regarding a highly diverse mycorrhizal potential for Douglas-fir and suggests that close scrutiny of EEB fruitbodies in relatively small permanent transects over time can be used to predict species diversity over a wider area. The need for developing regional monographs and keys to the larger ectomycorrhizal genera is also addressed.