Abstract: The present study was conducted to determine the isolation, identification and characterization of efficient oil degrading bacterial strains and to study the effect of different concentration of crude oil on the growth of bacterial strain. Two samples soil and water were collected from the crude oil contaminated areas for the isolation and characterization of efficient crude oil degrading strains. Sub culturing technique was employed to isolate 43 numerically dominant bacteria that had the ability to grow on 1.0% crude oil on nutrient agar plates. The isolates were then subjected to different concentrations of crude oil on nutrient agar, mineral salt agar media containing Phosphorous, Nitrogen and trace elements with glucose (PNTG) and without glucose (PER). These isolates showed rich growth on nutrient agar media along with crude oil. Out of 43 isolates 7 were able to grow up to 2.0% crude oil and were named as AA-1 to AA-7. These strains were also able to grow on mineral salt agar media with and without glucose but with different susceptibility to different concentrations of crude oil. Finally 3 prospective strains AA-1, AA-2 and AA-3 were selected for further studies. These strains exhibited good growth in PNTG containing 1.0% crude oil as evident by increase in Optical Density (OD) after every 24 h for five days. These isolated strains were identified by morphological and biochemical tests and were found to belong to genus Bacillus. These strains were subjected to shake flask transformation of crude oil in mineral salt media (PNTG) with glucose for 15 days. Marked change in crude oil colour was observed for these isolates, indicating their biodegradative ability. These isolated strains were able to use crude oil as the sole source of carbon and energy even under stressed environmental conditions. Thus these strains have bright potential for biodegradation of crude oil resulting in clean up of oil spills.