Method of decontamination of a hydrocarbon-polluted environment by the use of bacterial compositions. The method is a process of biological decomposition of the hydrocarbons using, as decontaminating active ingredients, bacterial compositions composed of one or more strains from among the following microorganisms: Azotobacter vinelandii 21, Pseudomonas sp.9, Pseudomonas sp.19, Pseudomonas sp.31 and Acinetobacter calcoaceticus 23. In the method, prior analysis of the chemical composition of the pollutants is essential in order to select, in accordance with this composition, the mixture of strains of the most active microorganisms from among the five mentioned above, taking into account the natural conditions of the polluted environment. The bacterial composition also contains inorganic salts supplying N and P, and additives needed for bacterial growth.The method is used to decontaminate hydrocarbon-polluted soils, fresh water, salt water, waters from technological processes and industrial waste waters or effluents.