[Translated from the Russian original published in Khimiko-Farmatsevticheskii Zhurnal, Vol. 55, No. 11, pp. 22–27, November, 2021.] Cladonia rangiferina is a bushy lichen of the genus Cladonia and has a multi-regional distribution. This plant contains usnic acid as the main biologically active substance and has been tested against some opportunistic microorganisms. Among the studied C. rangiferina extracts, only glycerol extracts obtained at an extraction temperature of 40°C were biologically active and only against Gram-positive microorganisms (S. aureus) and fungi (C. albicans). The antimicrobial activity of the extracts decreased if the extraction temperature was raised to 90°C. The results showed that C. rangiferina lichen could be a potential rich source of effective antimicrobial agents.