In the 1990 Clean Air Act Amendments (CAAA), Congress enacted acid deposition controls to reduce sulfur dioxide (SO 2 ) emissions by 10 million tons below 1980 levels utilizing a market-based emissions trading program. In recent years, research on the combined effect of SO 2 and nitrogen oxides (NO x ) strongly suggests that the CAAA of 1990 will not be adequate to ensure a recovery of sensitive ecosystems, such as the Adirondack mountains and other effects associated with the same pollutants, such as those observed in the Chesapeake Bay. New legislation is needed to further reduce, in the most cost-effective manner, SO 2 and NO x emissions to mitigate these continuing acid deposition effects. Senators Daniel Patrick Moynihan (D-NY) and Alfonse M. D'Amato (R-NY) recently introduced the Acid Deposition Control Act of 1997 (S. 1097) which requires an additional 50% reduction of SO 2 and a 70% reduction in the level of NO x emitted from electric utilities. The legislation accomplishes these reductions by lowering the existing emissions cap on SO 2 and by initiating a new cap-and-trade program for NO x . In addition, the Act directs the Environmental Protection Agency (EPA) to develop ecological objectives for those ecosystems that are particularly sensitive to acid deposition. These objectives are to be evaluated on a four-year basis with the results reported to Congress. If significant progress in achieving these objectives is not obtained, the Act directs the EPA to take appropriate policy actions.