Pay for Success: The First Generation provides a look at the ten Pay for Success projects that have launched in the United States–projects that have finalized contracts and financing, and initiated service delivery as of March 2016. It offers detailed comparison of U.S. PFS projects and synthesizes observations on the market’s development to date. It is informed by Nonprofit Finance Fund’s unique and central vantage point in the U.S. Pay for Success arena. This report pulls from PFS contracts and other publically available documents, interviews with stakeholders, and incorporates information and observations gleaned by NFF through its more than five years of experience as a field builder, funding intermediary for PFS project development, and investor. It examines project goals and project design; the partners and stakeholders involved; the underlying data, evidence, and evaluation plans; the governance and investment structures, including repayment terms and investor profiles; and project costs. The report also provides key definitions for some terms, in an effort to further a common language for the PFS eld.