The master’s thesis topic “The Ecological Ash Remediation Using Wood-Decaying Fungi” describes how to eliminate ash toxins and avoid raising the level of soil pollution using wood-decaying fungi, specifically the species Pleurotus ostreatus. The thesis aims to deepen knowledge about soil pollution by heavy metals, pesticides, polycyclic aromatic hydrocarbons (PAH) and polychlorinated biphenyls (PCBs) and possibility of their degradation by fungi. Research focuses on the cultivation of oyster mushroom on a wood substrate with the addition of a certain amount of ash. To achieve the goals, we used three production strains of oyster mushroom. The strains X12 and POSM are natural and the production strain 272 which was bred. The results of the work represent the research that describes the content of various chemical elements, especially the heavy metals, such as Ca, N, S, Al, Pb, Hg, Mn, Fe, Cu, As, Ni, Cd, Co. The content substances were determined on the basis of dried samples of fruiting bodies and substrate. Actual thesis deepens the knowledge in the field of mushroom reproduction and growing in the toxic environment. It also provides a detailed explanation of the Oyster mushroom cultivation possibilities. Finally, it defines the way of remediation of ash by mycofiltration effect and compares samples of various substrates.