Privacy, confidentiality, and security are largely taken for granted in physicians' offices. However, increasingly, physicians and insurance providers will be obtaining and exchanging information through the sophisticated resources available on the Internet and the World Wide Web (WWW, or the Web). Some of these resources will maintain the same privacy experienced in the office of a trusted clinician or in the reading room of a great library, but more often than not, while people are learning from the Web, the Web will be learning about them. The author describes a new type of file used by Web browsers (the “cookies” file) that may enable users to browse the Web more efficiently but that may also compromise the user's privacy. He then discusses exactly how abuses might occur if information obtained through cookies files is misused, particularly by health insurance providers. Finally, he considers privacy and confidentiality issues raised by computer-based medical records, and the role of the health care provider in maintaining confidential and helpful doctor-patient relationships in the face of rapid technological change and the pressures of managed care.