Google and Microsoft want to do the same thing for personal health that software such as Quicken has already done for people's personal finances. Google Health, which was released in May, and Microsoft HealthVault, which launched last October, allow consumers to store and manage their personal medical data online. Users will be able to gather information from doctors, hospitals, and testing laboratories and share it with new medical providers, making it easier to coördinate care for complicated conditions and spot potential drug interactions or other problems. Both Google and Microsoft will also offer links to third-party services like medication reminders and programs that track users' blood-­pressure and glucose readings over time.

Patients already have a legal right to copies of their medical data--information that they paid for and own. But in practice, that right is often difficult to exercise: patients must traipse from lab to hospital, waiting in line for photocopies of CT scans, prescription records, and discharge summaries. That's because many doctors still do not use electronic records, and others are unwilling or unable to transfer data to patients in electronic form. In a 2007 Wall Street Journal Online/Harris Interactive poll, only about a quarter of respondents reported having electronic records, generally in their doctor's offices; just 2 percent of all respondents said they had created and maintained medical records on their own computers, and just 1 percent reported using a "personal health record that is stored on the Internet." HealthVault and Google Health just may push doctors and hospitals to adopt electronic records at last.