This document, developed by the U.S. Environmental Protection Agency in response to a Congressional request, analyzes the environmental impacts, costs, and benefits of Senate Bill 172 (S.172). The bill, entitled the Acid Deposition and Ozone Control Act, is designed to address multiple regional and national-scale health and environmental impacts associated with emissions from power generation. S.172 mandates year-round reductions in electric utility emissions of sulfur dioxide (SO(2)) and nitrogen oxides (NO(X)). SO(2) emissions from utilities are to be cut in half, compared to the levels allowed by Title IV (Acid Deposition Control or 'Acid Rain Program') of the Clean Air Act Amendments of 1990 (CAAA). Annual utility emissions of NO(X) are to be reduced by about 60 percent below the levels projected to result from Title IV, with a somewhat greater reduction in the late spring and summer months when NO(X) contributes to ozone formation.