ABSTRACT Monitoring is a common, if generally implicit, part of spill response. However, there are no general guidelines for designing and carrying out spill response monitoring. With a few notable exceptions, as in shoreline assessments, monitoring rules are made up as the response progresses. Important rules of monitoring, such as those concerning adequate controls, are often left out or remain ill-defined, leading to unjustified product claims. As a result, there is often considerable debate and confusion about the effectiveness of protection and cleanup actions as well as the need to move on or terminate the response. A framework has been developed to help make monitoring an explicit process in spill response management. This framework forces (1) clear identification of the objectives of prevention and cleanup strategies, (2) selection of meaningful and useful end points, to quickly document effectiveness, (3) an appropriate strategy (statistical or otherwise) for collecting and reporting needed feedback information, (4) an often-overlooked quality assurance/quality control plan, (5) a data or information management plan, and (6) confirmation that a decision was (or was not) made based on monitoring results. The most important aspect of an explicit monitoring plan is that it forces not only clear definition of “how clean is clean enough,” but also how this measure will be operationally documented. Elements of this process are indeed covered in many past responses and in some recent documents. Nevertheless, there is a critical need to develop additional rapid response tools for chemistry, biology, and toxicology and for a more thorough operational monitoring guide for spill response.