This study investigated the biological removal of heavy fuel oil in a bench­scale biopile reactor inoculated with three microbial strains (Acinetobacter junii/jonsonii A­1, Acinetobacter baumanii/calcoaceticus N­1, and Pseudomonas aerognosa NW­6). In addition, a respiration test was conducted to measure the aerobic degradation rate by the strains. In the bench biopile, about 8.7% removal of total petroleum hydrocarbons (TPHs) was found in the absence of strains, whereas more than 50% was degraded in the presence of strains within 15 days at an initial TPHs concentration of 5,860 mg/kg. Under the same conditions, the microbial population increased up to 4.2×106 CFU/g (2.1 times higher) with strains after 15 days, whereas the microbial population increased only 1.25 times without strains. As a result of respiration test, it was found that oxygen utilization rate ranged from 0.042 to 2.09% O2/hr. These results suggest that the microbial strains could be used to improve bioremediation of fuel oil­contaminated soils with the biopile system.