Google's online filing cabinet for medical records opened to the public Monday, giving users instant electronic access to their health histories while reigniting privacy concerns.

Called Google Health, the service lets users link information from a handful of pharmacies and care providers, including Quest Diagnostics labs. Google plans to add more.

Similar offerings include Microsoft Corp.'s HealthVault and Revolution Health, which is backed by AOL co-founder Steve Case.

Google Health differentiates itself from the pack through its user interface and things like the public availability of its application program interface, or API, said Marissa Mayer, the Google executive overseeing the service.

Mary Adams, 45, a Cleveland Clinic patient who participated in the Google Health pilot, said that she was initially concerned about the privacy of her medical information.

Still, she felt safe enough to enroll and has been using the service for about six months, linking it with an online health management tool from the Cleveland Clinic and adding information on prescriptions and doctors to her online profile.

"I hate pieces of paper lying around my house, so I love the fact that i can log on with my normal Google login info and see everything at a glance," she said, adding that with its public availability she'll try to get her sister to use it.

The service, still a non-final "beta" version, does not include ads. But Mayer said Google doesn't plan to start placing them to support the site. A search box on Google Health pages leads to standard Google search results pages, where there are advertisements.

Besides importing records from providers, users can enhance their password-protected profiles with details such as allergies and medications, they can search for doctors and they can locate Web-based health-related tools.

Mountain View-based Google Inc. views its expansion into health records management as logical because its search engine already processes millions of requests from people trying to find information about injuries, illnesses and recommended treatments.

Before this public launch, Google stored medical records for a few thousand patient volunteers at the nonprofit Cleveland Clinic.

The health venture provides fodder for privacy watchdogs who believe Google already has too much about the interests and habits of its users in its logs of search requests and its vaults of e-mail archives.

Pam Dixon, executive director of the World Privacy Forum, said services like Google Health are troublesome because they aren't covered by the Health Insurance Portability and Accountability Act, or HIPAA.

Dixon's group issued a cautionary report on the topic in February on such third-party services.

Passed in 1996, HIPAA set strict standards for the security of medical records. Among other things, the law requires anyone seeking a patient's records by subpoena to notify the patient and give the patient an opportunity to fight the request.

By transferring records to an external service, patients could unwittingly make it easier for the government, a legal adversary or a marketing concern to obtain private information, Dixon said.

"We are in uncharted territory here. A privacy policy, I don't think, is enough to protect what needs to be protected in a doctor-patient record," Dixon said.

Mayer said, however, that users medical records "are generally speaking as safe with Google as they would be with a HIPAA-regulated entity."

During a webcast Monday, she said users' health information is stored at Google's "highest level of security" on computers that are more secure than those used for the company's search functions.

Mayer said in an interview with The Associated Press that Google will not aggregate users' health information across services so activity on the health service will not show up in search results.