A market-based cap-and-trade system is at the heart of many legislative proposals for addressing climate change, and a properly functioning market will be critical to achieving environmental goals. In the aftermath of the energy price spike of 2008 and the financial crisis of 2008-2009, concerns about the risks associated with the creation of a new market for carbon in the U.S. have moved from being a minor consideration to a defining issue. This series of papers and workshops explores key issues and options involved in regulating any U.S. carbon market, including lessons learned from existing cap-and-trade schemes in the U.S. and abroad, unique challenges, and ways to build upon best practices for market regulation.