Given the increasing importance assumed by online health forums as a form of doctor-patient communication, this study describes the types of dialogic and polylogic interactions that develop in this type of communicative event, focusing on a corpus of threads drawn from an “Ask a Doctor” forum in the area of cardiology. Adopting a discourse analytical approach, the investigation illustrates how these forums may popularize biomedical knowledge. After describing the shifting conceptualization of popularization, we present a new conceptualization of Web 2.0 popularization which we call “oblique popularization”, as it is indirect, user-generated, dialogic and polylogic, and targeted. In particular, this study characterizes the online health forum as a Web 2.0-style popularization tool. It does so not only because biomedical information communicated to a single inquirer is also available to the whole population, but also because the function of the online forum as a medium of popularization is discursively acknowledged by the participants. The study also explores what explanatory tools (such as definitions, analogies, exemplifications, and generalizations) are used by the experts to present complex or technical information. The analysis shows that biomedical information is circulated on a health forum by a complex network of participants, and that e-patients’ posts may also serve as prompters of popularization