The goal of this project was to suggest principles of professional ethics for the online provision of clinical mental health services that could guide both clinicians who provide and patients who receive such services. A joint committee of the International Society for Mental Health Online (ISMHO) and the Psychiatric Society for Informatics (PSI) was formed. Discussion and development of these principles took place online. A set of principles was produced and endorsed by ISMHO on January 9, 2000, and by PSI on May 13, 2000. The principles involve informed consent (about the process, the clinician, the potential risks and benefits, safeguards, and alternatives), standard operating procedure (competence, legal requirements, the structure of the services, evaluation, multiple treatment providers, confidentiality, records, and existing guidelines), and emergencies (procedures and local backup). This project demonstrates that traditional principles of professional ethics can be extended to online services, that comprehensive ethical principles can be developed by groups that cross disciplinary and national boundaries, and that productive collaboration can take place entirely online; and suggest that online clinicians have the potential to regulate themselves.