An oil spill caused by ship, pipeline, or oil platform disaster is a significant threat to marine and shoreline ecosystems. Booms and skimmer systems have proven to be ineffective responses. Chemical dispersants have proven effective, but they do not work on weathered oil and may pose health hazards. To reduce the toxicity and enhance biodegradation of the dispersed oil, biosurfactants can be used as opposed to chemical surfactants for open water oil spill response applications. This study examined the effect of rhamnolipid biosurfactant, JBR 425(TM), on the dispersion and biodegradation of BRENT crude oil spilled on surface water. Crude oil dispersion and biodegradation experiments were conducted according to the methods currently required for listing dispersants on the National Contingency Planning schedule (USEPA 1996). (Abstract shortened by UMI.)