Abstract
This article addresses 2 questions. First, how useful is adult patients' information about health and healthcare when they use the Internet for a "health checkup"? We find that patietns' reports are very strongly associated with medical record information for blood pressure, cholesterol, and blood glucose. Second, what are the biases in information from Internet respondents? Although we find that "health checkup" Internet users seem to be representative for patients in actual practice, much more research will be needed to fully address this question.