Abstract: The object of the invention is a method for improving the impregnability of refractory wood species by pretreatment with fungi of the genera Trichoderma o Gliocladium or with weakly wood-degraging fungi. The pretreatment comprises a thermal treatment of the wood, the addition of a nutrient medium as well as an incubation phase to promote fungal growth. The incubation phase is stopped when the desired depth of penetration of the fungus is reached. The wood is subsequently impregnated with a wood impregnating agent. The typical result of the fungal pretreatment is an incarease in the depth of penetration of the impregnating agent to a depth of penetration of 5 mm to 30 mm required depending on the intended use.