The United States Oil Pollution Act of 1990 (OPA) was enacted to reduce the probability of oil spills in U.S. waters. A key provision of the legislation enables recovery of damages for restoration of injured natural resources and lost services due to oil spills. The National Oceanic and Atmospheric Administration (NOAA) de,eloped regulations that set out a process for determining the appropriate type and scale of restoration actions to accomplish this goal. The restoration plan developed through this process is the basis for an economic claim for natural resource damages. The regulations recognize that various methods, including environmental models, may be used in identifying and quantifying injuries to natural resources and losses of their services and in developing a restoration approach for these injuries, Rather than designating particular assessment measures, NOAA requires each trustee to decide which methodologies are appropriate for each incident, given its particular facts and circumstances. Any procedure chosen must meet the standards in the rule: it must provide information useful for determining restoration needed for an incident, the cost of the method must be commensurate with the quality and quantity of information it is expected to generate, and, of particular significance here, the method must be reliable and valid for the particular incident. This paper describes how methods are selected, how they might be used, and what legal standards would be applied should these methods be used as evidence in litigation,