Bioremediation is a process by which microoorganisms degrade or transform the environmental contaminants into less toxic forms. A wide variety of bacterial and fungal genera are known to be capable of degrading, and in many cases, completely mineralizing chemical substances present in petroleum products at present. Three types of bioremediation are predominant in the industry: natural attenuation, biostimulation and bioaugmentation. Selecting the most appropriate strategy to treat a specific site can be quided by considering three basic principles: the amenability of the pollutant to biological transformation to less toxic products, the accessibility of contaminant to microorganisms (bioavailabilty) and the opportunity for optimization of biological activity. Microbial activity is affected by a range of environmental factors, including nutrients, moisture content, pH, temperature, and oxygen concentration. Different aspects of bacterial degradation of petroleum contaminants in soil and how to improve the efficiency and reproducibility are discussed in this review.