BackgroundMany health information providers on the Internet and doctors with email accounts are confronted with the phenomenon of receiving unsolicited emails from patients asking for medical advice. Also, a growing number of websites offer "ask-the-doctor" services, where patients can ask questions to health professionals via email or other means of telecommunication. It is unclear whether these types of interactions constitute medical practice, and whether physicians have the ethical obligation to respond to unsolicited patient emails.ObjectiveTo improve the quality of online communication between patients and health professionals (physicians, experts) in the absence of a pre-existing patient-physician relationship or face-to-face communication, by preparing a set of guiding ethical principles applicable to this kind of interaction.MethodsSystematic review of the literature, professional, and ethical codes; and consultation with experts.ResultsTwo different types of patient-physician encounters have to be distinguished. "Traditional" clinical encounters or telemedicine applications are called "Type B" interactions here (Bona fide relationship). In comparison, online interactions lack many of the characteristics of bona fide interactions; most notably there is no pre-existing relationship and the information available to the physician is limited if, for example, a physician responds to the email of a patient who he has never seen before. I call these "Type A" consultations (Absence of pre-existing patient-physician relationship). While guidelines for Type B interactions on the Internet exist (Kane, 1998), this is not the case for Type A interactions. The following principles are suggested: Physicians responding to patients' requests on the Internet should act within the limitations of telecommunication services and keep the global nature of the Internet in mind; not every aspect of medicine requires face-to-face communication; requests for help, including unsolicited patient questions, should not be ignored, but dealt with in some appropriate manner; informed consent requires fair and honest labeling; health professionals and information providers must maintain confidentiality; health professionals should define internal procedures and perform quality control measures.ConclusionsDifferent media are appropriate at each point on the continuum between dispensing general health information and handling patient problems that would require the practice of medicine to solve. For example, email is a sufficiently capable medium for giving out general health information, while diagnosis and treatment usually requires at least advanced telemedical technology. Patients have to be educated that it is unethical to diagnose and treat over the Internet in the absence of a pre-existing patient-physician relationship, and if the interaction is limited to a single email. More research is needed to establish more evidence regarding situations in which teleadvice is beneficial and efficient.