A number of species of wood decay fungi important for the damage they cause to timber and timber products in Korea were cultured. Trametes versicolor, which is one of the most important, was also cultured from a collection made in the UK and likewise the ascomycete Daldinia concentica was obtained for comparative studies. In the initial testing of the effectiveness of the two wood preservatives, ammoniacal copper quaternary (ACQ) and copper azole (CuAz) preserve injected blocks of Japanese Red Pine and Yellow Poplar were inoculated with T versicolor, Pleurotus ostreatus and D. concentrica. Weight loss(%) of the wood blocks showed that Japanese Red Pine possessed greater natural resistance to decay by the white rot basidiomycete fungus T versicolor, than to the white rot ascomycete D. concentrica. The results for Yellow Poplar were the opposite. It was also found that both preservatives had an inhibitory effect on all three test fungi regardless of tree species. Furthermore ACQ was the most effective preservative in relation to T versicolor, which is the most damaging wood decay fungus in Korea. It has also been found that the absorption of the preservatives by the two different wood types differed with Yellow Poplar exhibiting a slightly greater absorption than the Japanese Red Pine, which might be a result of differences in the anatomical structure of the woods. Fungal biomass was also determined using chitin and ergosterol assays. The results regarding levels of decay caused by T versicolor, P ostreatus and D. concentrica are in close agreement with the weight loss determinations. The assays also confirmed the effectiveness of the copper based preservatives. The application of Scanning Electron Microscopy (SEM) has allowed observations on the damage caused by the test fungi to the untreated blocks of the two wood species and the reduction in damage on blocks treated with the preservatives. Linked studies using the SEM and Atomic Force Microscopy have demonstrated differences in the micromorphology of the hyphal tips of the test fungi.