The Regional Greenhouse Gas Initiative (RGGI) is the nation's first mandatory cap-and-trade program for greenhouse gas (GHG) emissions. As of 1 January 2012, RGGI involves nine states - Connecticut, Delaware, Maine, Maryland, Massachusetts, New Hampshire, New York, Rhode Island, and Vermont. The RGGI cap-and-trade system applies only to carbon dioxide (CO2) emissions from electric power plants with capacities to generate 23 megawatts or more-approximately 168 facilities. The RGGI emissions cap took effect 1 January 2009. This book provides an overview of the RGGI cap-and-trade program and the participating RGGI states, with a discussion on select issues raised by RGGI that may be of interest to policy-makers who are considering developing a federal program.