Trust in the doctor, an essential condition of medical practice throughout its history, appears to be considered as an outdated value, destined to extinction. In his work, Pellegrino analyzes the epistemological, empirical and conceptual basis of trust in professional relationships, the reasons for its weakening in an ethics of distrust, and he presents his philosophical proposal, which recovers and reappraises the fidelity to trust placed in the doctor-patient relationship, as an essential virtue for an appropriate ethical behaviour in the practice of medicine as in a moral community.