Are public health interventions ethical? How many of us, as public health professionals, have ever asked this question explicitly? How many of us feel qualified to answer it? I have practiced public health for fifteen years, with all the requisite academic credentials. I have, however, no formal training in ethics. And, while I have not infrequently broached the “ethics” of decisions, these discussions have never been couched within any well-defined conceptual framework. I suspect that my experience is not unusual. There has been a veritable renaissance in the field of medical ethics over the past 25 years. This began with clinical research, where independent ethical review is now an essential element of any study involving human subjects. This trend is extending directly into clinical practice. Many hospitals now have a resident ethicist. Typically this is a clinician with a special interest and training in medical ethics who is consulted both on policy and on difficult cases. Public health has lagged behind. Ethics does not form part of the core training of public health physicians or, I suspect, other public health professionals. Nor has it become part of our professional lives. How many of us have consulted an ethicist regarding a public health intervention? Public health practice is substantially different from clinical medical practice. The ethical frameworks that have been developed for clinical medicine should not be applied uncritically to public health. Ross Upshur’s timely article in this issue of the CJPH will, I hope, mark the beginning of a more rigorous examination of the ethics of public health interventions. This is important because, in the absence of well-defined public health ethics, clinical ethics will fill the vacuum and be applied and misapplied to public health practice. Why are public health ethics different from clinical ethics? I think that the critical difference derives from the population focus of public health versus clinical medicine’s focus on the individual. The therapeutic contract in clinical practice is with the individual. Although the interests of the individual may be best served within a broader context (e.g., family practice), ultimately the clinician has what Upshur calls a “fiduciary role” to act in the best interests of the individual patient, regardless – with some exceptions – of what is best for the society as a whole. This contract is legitimized by the informed consent of the patient or someone duly authorized to consent on the patient’s behalf. Public health’s therapeutic contract is with society as a whole, legitimized by the policies and legislation of government. Public health programs and interventions are justified by their net benefit to the population as a whole, rather than a benefit for each and every individual. The “fiduciary role” is with society as a whole. Public health may intervene with an individual in a manner that is not perceived by the individual as in his or her personal best interests. This action is legitimized by the powers invested in public health officials, subject to the protections of our legal system. Clinical practitioners may only intervene with an individual in a manner perceived by the individual as in his or her best interests and legitimized by informed consent. There are some exceptions to this clinical contract when clinicians as asked to play a quasi public health role. An example of this is the requirement that physicians report to government individuals with medical conditions that may make them unable to safely operate a motor vehicle. There are important differences in patterns of practice – public health versus clinical practice – that have significant implications for the question of standards of evidence. In clinical practice, the patient seeks out the health care provider because they want a service, usually because they have a problem. The health care provider’s obligation is to offer the patient the best treatment available. If there is sound evidence for a particular treatment, this is what should be offered. If, as is often the case, there is no high-quality evidence, the practitioner may well offer a reasonable treatment, based on a very flexible standard of evidence. The patient may then accept or reject the treatment offered. So long as the recommendation is reasonable and the consent is informed, the clinical contract is fulfilled. Clinical interventions are ultimately held to a standard of benefit that has both objective (based on what medical science thinks is reasonable) and subjective (based on what the patient is prepared to accept) components. In public health practice, the public health practitioner usually seeks out the patient, because the practitioner believes that the patient has a problem. The patient has not asked for the service and may not be in a position to reject the treatment offered. This means that public health interventions must be held to a standard of benefit that is strictly objective. The absence of informed consent raises the evidentiary bar. I do not mean to imply by this that public health interventions must always meet the highest standards of objective evidence, i.e., randomized clinical trial or so-called level A evidence. Like all health providers, public health practitioners must live with uncertainty and make decisions based on an assessment of the best available evidence. Furthermore, I believe that it is the nature of the threat, as well as the nature of the intervention, that determines the appropriate level of evidence. With most communicable disease threats, for example, the threat is immediate and the window of opportunity for effective intervention is narrow. Public health must act quickly if it is to act at all. In so doing, we must be prepared to make mistakes. Procrastination, while waiting for better evidence, will often mean that any opportunity to act effectively is lost. Society expects us to act in response to a Schabas Associates Inc., Toronto, ON, E-mail: schabas.assoc@sympatico.ca