The Emission Standards Division (ESD) of the U.S. Environmental Protection Agencys (EPAs) Office of Air Quality Planning and Standards (OAQPS) is developing a proposal to implement New Source Performance Standards (NSPS) on compression ignition (CI) stationary internal combustion engines by June 29, 2005. This proposal, which is in response to a consent decree and is under the authority of Section 111(b) of the Clean Air Act, will address emissions for nitrogen oxides (NOx), sulfur dioxide (SO2), particulate matter (PM), nonmethane hydrocarbons (NMHC), and carbon monoxide (CO) from new CI engines. The requirements of the NSPS generally follow the nonroad diesel engine rule developed by EPAs Office of Transportation and Air Quality (OTAQ). The proposed NSPS contains requirements for owners, operators, and manufacturers of stationary CI engines. The proposed NSPS requires manufacturers to certify their 2007 and later model year stationary nonemergency CI engines to the Tier 2, Tier 3, and Tier 4 certification emission standards for nonroad diesel engines for all the pollutants (except SO2). To support EPAs development of these standards, EPAs Innovative Strategies and Economics Group (ISEG) has conducted an economic impact analysis (EIA) to assess the potential costs of the rule. This report documents the methods and results of this EIA.