For conservation of biodiversity and nature protection ecologically safe methods for purification of areas polluted by oil are necessary. Oil pollution inhibits microbiological and biochemical processes in soil and water, causes destructive changes in natural ecosystems and, at high concentration, results in death of living organisms. One of the most important factors for purification of environment polluted by oil is microbial activity. Microbiological methods of purification, when pure cultures of micro-organism decomposers adapted to pollution are added to natural microbial communities, are preferable. Only native micro-organisms which are not aliens to the natural ecosystem can be effective. In Ukraine, screening has been carried out of strains which can decompose oil. The source of these strains has been freshly isolated and collected cultures of hydrocarbon-oxidizing bacteria isolated from soil and water in various soil and climatic regions and oil deposits within the country. Most oil-oxidizing bacteria able to assimilate hydrocarbons as the only source of carbon and energy belong to the Gram-positive nocardioform genus Rhodococcus and the Gram-negative genera Acinetobacter and Pseudomonas. It has been possible to create a stable association of active hydrocarbon-oxidizing strains of hydrophobic and hydrophilic bacteria from different taxonomic groups with various metabolisms, but viable in unfavourable conditions. Strains used were selected taking into account maximum specific growth rate and specific effect on separate oil components. Using these selected cultures, a new oil-oxidizing ecologically safe biopreparation "Rodoil", is being developed, which works on the polluted environment in many ways. This preparation contains, in addition, fertilizers with balanced nitrogen, phosphorus, potassium, biostimulators, microelements and sorbent. Results show that efficiency of oil biodegradation using "Rodoil" is 30-40% greater than present commercial preparations.