OBJECTIVE: To describe people who use the internet for healthcare information and compare them to those who do not, based on physician visits, health status, and healthcare attitudes. METHODS: Analyses were based on a 12-page questionnaire mailed to US adults in 1999. A total of 19,863 (54.9%) responses were received. Respondents were nationally representative based on age, gender, race, and geographic region; results were subsequently weighted and projected to the US population. Participants were asked how often in the past six months they received healthcare information from the internet. Responses were on a five-point scale from “not at all” to “very frequently” and were subsequently categorized as not at all (1), occasional (2-3), and frequent (4-5). RESULTS: Three quarters of the sample (149.4 million) reported never using the internet for healthcare information, 17% (33.1 million) reported occasional use, and 8% (16.9 million) reported frequent use. Internet users were more likely to young, female, better educated, and have higher incomes. Those who used the internet for healthcare information were more proactive consumers than non-users. They were more likely to ask doctors for prescriptions and to question physicians’ advice. These attitudes and behaviors held true for both frequent and occasional internet healthcare information seekers, but were even more extreme for the frequent seekers. CONCLUSION: Most American adults did not seek internet healthcare information. Those who frequency sought such information, however, were “cyberchondriacs.” When compared to the general population, they were less satisfied with their healthcare, were in poorer health, visited physicians and alternative health providers more often, missed more days of work due to poor health, and were likely to seek healthcare information from a variety of sources. They did not look like the typical healthcare consumer. Occasional users, however, were much more representative of those who typically seek healthcare information.