Context: The term eHealth is widely used by many individuals,academic institutions,professional bodies,and funding organizations.It has become an accepted neologism despite the lack of an agreed-upon clear or precise definition.We believe that communication among the many individuals and organizations that use the term could be improved by comprehensive data about the range of meanings encompassed by the term.Objective: To report the results of a systematic review of published,suggested,or proposed definitions of eHealth.Data Sources: Using the search query string “eHealth” OR “e-Health” OR “electronic health”,we searched the following databases: Medline and Premedline (1966-June 2004),EMBASE (1980-May 2004),International Pharmaceutical Abstracts (1970-May 2004),Web of Science (all years),Information Sciences Abstracts (1966-May 2004),Library Information Sciences Abstracts (1969-May 2004),and Wilson Business Abstracts (1982-March 2004).In addition,we searched dictionaries and an Internet search engine.Study Selection: We included any source published in either print format or on the Internet,available in English,and containing text that defines or attempts to define eHealth in explicit terms.Two of us independently reviewed titles and abstracts of citations identified in the bibliographic databases and Internet search,reaching consensus on relevance by discussion.Data Extraction: We retrieved relevant reports,articles,references,letters,and websites containing definitions of eHealth.Two of us qualitatively analyzed the definitions and coded them for content,emerging themes,patterns,and novel ideas.Data Synthesis: The 51 unique definitions that we retrieved showed a wide range of themes,but no clear consensus about the meaning of the term eHealth.We identified 2 universal themes (health and technology) and 6 less general (commerce,activities,stakeholders,outcomes,place,and perspectives).Conclusions: The widespread use of the term eHealth suggests that it is an important concept,and that there is a tacit understanding of its meaning.This compendium of proposed definitions may improve communication among the many individuals and organizations that use the term.