The purpose of the report is to summarize the most current information from the available literature for the mechanism of action of chemical dispersants (or how they work) for oil spills, variables that affect dispersant performance, evaluations of a variety of laboratory tests designed to assess the performance of dispersant agents, and a brief consideration of relationships between laboratory methods and field situations. In part, the book updates information on the preceding topics from earlier documents. Considerations are given to strengths and limitations of specific laboratory tests, including brief discussions of the applicability of their results for estimating dispersant performance in field trials or conditions encountered during real spill events. Finally, a modest attempt is made at providing recommendations for improvements in future laboratory testing.