Although significant steps have been taken over the last 15 years to reduce the size and frequency of oil spills, the sheer volume of petroleum consumed in the United States and the complex production and distribution network required to meet the demand make spills of oil and other petroleum products inevitable. Approximately 3 million gallons of oil or refined petroleum products are spilled into U.S. waters every year. Oil dispersants (chemical agents such as surfactants, solvents, and other compounds) are used to reduce the effect of oil spills by changing the chemical and physical properties of the oil. By enhancing the amount of oil that physically mixes into the water, dispersants can reduce the potential that a surface slick will contaminate shoreline habitats. Although called for in the Oil Pollution Act of 1990 as a tool for minimizing the impact of oil spills, the use of chemical dispersants has long been controversial. This report reviews the adequacy of existing information and ongoing research regarding the effectiveness of dispersants as an oil spill response technique, as well as the effect of dispersed oil on marine and coastal ecosystems. It includes recommended steps to be taken to better support policymakers faced with making hard choices regarding the use of dispersants as part of spill contingency planning efforts or during actual spills.