A person sometimes forms moral beliefs by relying on another person''s moral testimony. In this paper I advance a cognitivist normative account of this phenomenon. I argue that for a person''s actions to be morally good, they must be based on a recognition of the moral reasons bearing on action. Morality requires people to act from an understanding of moral claims, and consequently to have an understanding of moral claims relevant to action. A person sometimes fails to meet this requirement when she relies on another person''s moral testimony, and so there are moral limits on such reliance.