This paper investigates the information in corporate credit ratings. We examine the extent to which firms' credit ratings measure raw probability of default as opposed to systematic risk of default, a firm's tendency to default in bad times. We find that credit ratings are dominated as predictors of corporate failure by a simple model based on publicly available financial information (`failure score'), indicating that ratings are poor measures of raw default probability. However, ratings are strongly related to a straightforward measure of systematic default risk: the sensitivity of firm default probability to its common component (`failure beta'). Furthermore, this systematic risk measure is strongly related to credit default swap risk premia. Our findings can explain otherwise puzzling qualities of ratings.