The credit rating agencies (CRAs) were an important component of the subprime mess. This article describes what the CRAs are, what they do, what roles they play, and how they fit into the regulatory system. It outlines the types of mortgage securities that the CRAs rate and outlines the evolution of the subprime mess. It then assesses three prime suspects in the CRAs' problems: incentives, ignorance, and stress. The author concludes that all three factors were important, that public officials were slow to react, and that additional safeguards have been put into place to prevent such problems in the future.