This document presents a comprehensive review of the use of commercial bioremediation products used to treat oil spills in all environments. The literature assessed includes peer-reviewed articles and reports from companies, government agencies, and cleanup contractors engaged in responses to oil spills. Though estuarine environments are the primary focus, marine shorelines, terrestrial environments, fresh waters, and wetlands are frequent candidates for bioremediation of spilled oil, and information on these ecosystems is contained in the review. This report will be useful for oil spill responders (e.g., on-scene coordinators and response contractors) to better understand the feasibility of bioremediation technology and to aid in bioremediation products selection. Section 1 provides an overall introduction of the background and the scope of this review. Section 2 presents an in-depth review of field tests of bioremediation products based on literature from peer-reviewed journal articles, books, and conference proceedings. Section 3 evaluates oil bioremediation products identified in the gray literature, i.e., government agency reports and vendor/service provider reports. Section 4 presents conclusions and recommendations based on the reviewed information. The reviewers arrived at the following conclusions. (1) According to the peer-reviewed literature, bioaugmentation appears to have little benefit for the treatment of spilled oil in an open environment. Microbial addition has not been shown to work better than nutrient addition alone in many field trials; however, vendor case studies seem to suggest that application of bioaugmentation products could still have some potential in the treatment of specific oil components, isolated spills in confined areas, or certain environments where oil-degrading microorganisms are deficient. Unfortunately, the evidence for such a conclusion is not strong and in most if not all cases is scientifically deficient. (2) Biostimulation has been shown to be a promising tool to treat certain aerobic oil-contaminated shorelines. One of the key factors for the success of a biostimulation approach is to maintain an optimal nutrient level in the interstitial pore water. In general, commercial oleophilic nutrient products have not shown clear advantages over common agricultural fertilizers in stimulating oil biodegradation. Effects of nutrients are also highly site-specific. For example, the availability of oxygen rather than nutrients is often the limiting factor in wetlands, where addition of nutrient products has not been successful in enhancing oil biodegradation. (3) The extreme uncertainty associated with the efficacy of bioremediation agents is due in large part to the poorly designed field tests that have been conducted to demonstrate efficacy. Much of the work reported in literature either lacked proper controls and quality assurance, or the data were incorrectly analyzed. If there is any hope for advancement of commercial bioremediation, experiments based on sound scientific principles are needed. Unfortunately, due to the extreme resource intensiveness of field studies, the benefit accruing to testing any bioremediation agent is only applicable to the one product being tested. Available at http://www.epa.gov/ORD/NRMRL/pubs/600r04075/600r04075.htm