BACKGROUND: Oil spills are a frequent source of environmental contamination. As a consequence, remediation of soils, waters and sediments is a great challenge in this area of research. This study aims at using a new type of soil bioreactor (13 L bench-scale and 800 L pilot-scale) to treat tropical soil contaminated with petroleum. Additionally, it includes the evaluation of the effectiveness of two auxiliary techniques: bulking agent addition (sawdust) and biostimulation using two different nitrogen sources (sodium nitrate and urea). RESULTS: The best result in bench- and pilot-scale bioreactors were reached when using urea as a nitrogen supplement and bulking agent addition. Removal of 20 to 35% of total petroleum hydrocarbon (TPH) was achieved within 42 days. Themolecular fingerprinting performed with 16S-PCR analysis associated with denaturing gradient gel electrophoresis (DGGE) was used to evaluate changes in the pattern of the bacterial community for all experimental conditions tested. The results revealed that the use of urea caused a smaller change in the dominant bacterial community structure than the treatments using nitrate, showing that this analysis can be a useful complementary tool to evaluate the impact of treatment strategies applied to hydrocarbon-contaminated soil. CONCLUSIONS: These new solid phase bioreactors showed satisfactory results in the tropical soil bioremediation process, proving that the homogenization system interferes with crude oil biodegradation efficiency. This new technology can be used as an isolated treatment as well as in association with other classically employed bioremediation technologies. © 2010 Society of Chemical Industry.