The paper studies the properties and chemical composition of birch fungus - Chaga, which contains a unique complex of biologically active substances and is used as a raw material for the production of drugs and biologically active additives. The components listed prove their antioxidant, immunomodulating, antiviral, antidiabetic, and cytotoxic properties. The paper specifies the application of chaga in such areas as medicine, agriculture and food industry. It analyses the way the method of grinding of plant raw materials might influence the quality of the resulting drugs, including the sustaining the biological activity. The results determined that the cryogenic grinding of chaga, which allows to preserve valuable substances of the fungus due to its grinding at low temperature in liquid nitrogen to be the most reasonable. The paper gives the analysis of the obtained dispersed phase by high performance liquid chromatography and atomic absorption spectroscopy. The results of the studies indicate an increase in the content of particular valuable components of the fungus in extracts of raw materials that have gone through the cryogenic grinding, compared with the extracts of raw materials obtained by the traditional grinding method. The data acquired can be of practical importance when chaga is used in medicine.