The Ukrainian Collection of Micro-organisms was established in the D.K. Zabolotny Institute of Microbiology and Virology, one of the oldest microbiological institutions in Ukraine. The working collection includes about 20000 strains of microscopic fungi (including yeasts), actinomycetes, bacteria (including streptomycetes, nocardia and coryneforms, lactic acid, phytopathogenic, methylotrophic and obligate marine bacteria, bacilli and cocci, free-living and symbiotrophic nitrogen-fixing bacteria, saprophytic bacteria of genera Pseudomonas, Comamonas, Stenotrophomonas, Burkholderia), and mycoplasmas. Of these, 3500 form the collection maintained on guarantee. A separate branch of the collection is a the Culture Collection of Sliding Bacteria of Odesa State University. The total collection resource represents 440 species from 115 genera of micro-organisms. These have been isolated from different ecological and geographical regions of Ukraine, including the radio-nucleotide contaminated area around Chernobyl, soils, air, water, rhizo- and phyllosphere of cultivated and wild plants, tissues and organs of man, animals, birds, fish and insects, food products, oil and gas fields, industrial and domestic sewage, diesel fuel, lubricants, and synthetic materials. Of particular interest are strains of Aspergillus parasiticus isolated from mummified human remains in the Kiev Pechersk Lavra monastery, and new species of marine associative bacteria of the genus Pseudoalteromonas, isolated from tissues of marine mussels. The collection is constantly enlarged with new isolates. The main directions of research are ecology, systematics, population analysis and biologically active substances produced by the microorganisms already mentioned. The collection maintains more than 300 strains of biotechnological importance, including lactic acid bacteria and aerobic Bacillus strains which are the components of probiotic preparations, microorganisms of Pseudomonas genus producing the new antibiotics which do not have analogues among the antimicrobic substances used in clinics; strains which produce enzymes, vitamins, amino-acids, polysaccharides, mycotoxins and other biologically active substances. For some of these all rights are reserved by patents. The strains are used in different fields of medicine, industry and purification of environment from pollution.