The aim of the paper was to determine the efficiency of petroleum hydrocarbons (PHs) degradation by developed bacterial consortium during bioremediation of oil-contaminated soils caused by accidental oil spills. The soil samples were collected from three different areas near the Bugruvate field of the Dnieper-Donets oil and gas region, Sumy region, Ukraine. The total petroleum hydrocarbon was determined by conducting measurements using a gravimetric method. Gas chromatographic analysis was performed for determination of polycyclic aromatic hydrocarbons. The level of oil contamination follows an increasing preferential order: Sample 1 < Sample 2 < Sample 3 (5, 10 and 15 g∙kg-1, respectively). The soil samples comprised different concentrations of PHs including n-alkanes, fluorine, anthracene, phenanthrene, pyrene, toluene, xylene, benzene and other PHs. The results of research indicated that the maximum oil degradation rate at the level of 80% was set at Cin within 4–8 g∙kg-1 and τ = 70 days, under natural condition. In order to improve the efficiency of bioremediation of oil-contaminated soils, bioaugmentation was performed using the developed preparation of such bacteria and fungi strains as Pseudoxanthomonas spadix, Pseudomonas aeruginosa, Rhodococcus opacus, Acinetobacter baumannii, Bacillus cereus, Actinomyces sp., Mycobacterium flavescens. The results showed 100% of oil concentration was assimilated after 20, 25 and 35 days for the soil samples with initial hydrocarbon concentrations at the level 5, 10 and 15 g∙kg-1, respectively. The bacterial consortium application (bioaugmentation) exhibited high efficiency compared to the indigenous microflora in the oil biodegradation. The optimal growth condition for the bacteria in this study can be set as follows: pH = 3–11, wide temperature range 0–35°C
