This paper investigates the new and unique medium of the Internet as a source of information about health. The Internet is an inherently interactive environment that transcends established national boundaries, regulations and distinctions between professions and expertise. The paper reports findings from a qualitative study of households who routinely used the Internet to access health information and examines how it affected their health beliefs and behaviours. The public use of previously obscure and inaccessible medical information is placed in the context of the debate about deprofessionalisation. It is shown that it is the users of Internet information rather than authors orprofessional experts who decided what and how material is accessed and used. It is concluded that the Internet forms the site of a new struggle over expertise in health that will transform the relationship between the health professions and their clients.