In a wide ranging paper the author, a barrister, considers medical ethics in the context of divided loyalties, particularly those of a doctor employed by the National Health Service and those of doctors in occupational medicine. He argues for more specific professional codes of medical ethics, especially in relation to the need to obtain patients' explicit consent before medical details are transmitted to third parties. On the thorny question of when, if ever, can the good of society override the doctor's special duty to his patient of confidentiality, he urges medical organisations to be more explicit at least on how members can set about resolving such dilemmas - mere assertion that a problem exists and that individual doctors must resolve it according to their consciences is not good enough, he says. Extolling honesty and openness as fundamental values he ends by suggesting that part of a binding code of medical ethics might be a requirement that doctors display in their waiting rooms information about their personal moral stances concerning major dilemmas of medical ethics. The paper was given as the Lucas lecture under the aegis of the Royal College of Physicians' Faculty of Occupational Medicine, in whose journal it is also published.