This paper models the strategic interaction between a rating agency, a banking sector and a bank regulator who lacks information about bank asset risk. The regulator can either (1) make bank capital requirements contingent on credit ratings; or (2) set rating independent capital requirements. Truthful ratings provide efficiency gains because they allow the regulator to constrain high risk bank investment without simultaneously reducing overall investment volume. However, if collusion between the rating agency and the bank corrupts rating quality, rating independent regulation enhances welfare. The welfare benefi ts are largest if regulators maintain rating contingent capital requirements and discipline rating agencies.