There has been a rapid growth in the number of articles using Internet data sources to illuminate health behavior. However, little has been written about the ethical considerations of online research, especially studies involving data from Internet discussion boards. Guidelines are needed to ensure ethical conduct. In this article, the authors examine how a youth-focused research program negotiated ethical practices in the creation of its comprehensive health site and online message board. They address three situations in which ethical predicaments arose: (a) enrolling research participants, (b) protecting participants from risk or harm, and (c) linking public and private data. Drawing on the ethical principles of autonomy, nonmaleficence, justice, and beneficence, the authors present practical guidelines for resolving ethical dilemmas in research on Internet communities.