Credit Guarantee Schemes (CGSs) are a widely used policy tool to ease access to finance by SMEs, which, in some countries, ramped up in the aftermath of the 2008-09 financial crisis. The present study aims to improve understanding about the role, impact and sustainability of CGSs, by investigating their characteristics along several dimensions, such as the ownership structure and funding, the legal and regulatory framework, and the operational characteristics of the schemes, including types of services, eligibility criteria, guarantee assignment process and credit risk management. The study explores these dimensions, using detailed examples from OECD and non-OECD countries. It identifies structural and emerging challenges for the financial sustainability and the financial and economic additionality of these schemes, in a rapidly changing economic and regulatory environment. The study investigates in particular the case of Mutual Guarantee Schemes, which are created by borrowers in order to improve their access to finance.