Previous measures of OPO performance based on population counts have been deemed inadequate, and the need for new methods has been widely accepted. This article explains recent developments in OPO performance evaluation methodology, including those developed by the SRTR. As a replacement for the previously established measure of OPO performance--donors per million population--using eligible deaths as a national metric has yielded promising results for understanding variations in donation rates among the donation service areas assigned to each OPO. A major improvement uses "notifiable deaths" as a denominator describing a standardized maximal pool of potential donors. Notifiable deaths are defined as in-hospital deaths among ages 70 years and under, excluding certain diagnosis codes related to infections, cancers, etc. A most proximal denominator for determining donation rates is "eligible deaths," which includes only those deaths meeting the criteria for organ donation upon initial assessment. Neither measure is based on the population of a geographic unit, but on restricted upper limits of deaths that could be potential donors in any one locale (e.g., hospital or OPO). The inherent strengths and weaknesses of metrics such as donors per eligible deaths, donors per notifiable deaths, and number of organs per donor are discussed in detail.