From samples of stained yellow cedar wood, Chamaecyparis nootkatens is (D. Don) Spach, collected at three different localities on the British Columbia coast, isolation studies consistently yielded two members of the group Fungi Imperfecti. Reinoculation of these fungi into sound wood produced black stain similar to that found in nature. In addition to these Deuteromycetes, three basidiomycetous fungi, Poria weirii Murr, Poria asiatica (Pilát) Overholts and Xeromphalina campanella (Batsch. ex Fr.) Kühner and Maire, were isolated. Of these the Poria species are believed to be first records for the host. Studies on Petri plates revealed no marked antagonism between the two Deuteromycetes and P. weirii. The two deuteromycetous fungi gave positive reactions on gallic and tannic acid agars, demonstrating the production of the enzyme extracellular oxidase. Two series of yellow cedar beams were respectively inoculated with macerated cultures of the Deuteromycetes by means of a special technique described. This technique produced exceptionally rapid and uniform fungal growth in comparison to that obtained under standard cultural conditions. Inoculated beams were subjected to weight and strength loss tests, in comparison to control beams. Weight losses of 0.17 percent and 8.40 percent respectively were noted for the two fungi. No significant difference in impact modulus of rupture values was detected between test and control for either fungus. Significance of experimental results is briefly discussed and recommendations for further study suggested. / Science, Faculty of / Botany, Department of / Zoology, Department of / Graduate