OBJECTIVES: Use of the Internet and email for health care information has attracted widespread attention. Available estimates of the prevalence of Internet use are widely variable - between 35% and 85% of the U.S. population are said to use the Internet for health, for example. Little information about the effects of Internet use on health care use is available. METHODS: We report results from a careful survey of a representative sample of the U.S. adult population (N=8,935; response rate=69%), which asked a range of questions about Internet and email use for health care and its impacts. RESULTS: In a carefully designed survey with a statistically strong sample, Internet use rates are much lower than frequently reported. For example, 32% of respondents said that they had used the Internet for information or advice about health or health care in the past year. 5% said that they had emailed a physician or other health care provider. Internet users frequently say that Internet use improved their understanding of health issues, but the impacts of the Internet on actual health care decisions and the number of visits and contacts with physicians are small. Use of the Internet for prescription drugs is also limited. CONCLUSIONS: Internet and email use for health care is less common than frequently reported in the media. There may be populations that could gain useful information from the Internet, but that are not now currently using it. If the Internet is to have a strong impact on use of the health care system, additional advances will be required current implementations of Internet sites and technology are not perceived by patients as having strong impacts on care use.