Americans increasingly are turning to the Internet for information about their health, with 80 percent of Internet users searching online for details about illnesses, potential treatments and other medical information, a new study has found.

Although Internet users don't research such issues frequently, 93 million Americans have searched at least once for health information, according to a survey released Wednesday by the Pew Internet & American Life Project.

That makes health research one of the most popular online activities -- behind the 93 percent of Internet users who send and receive e-mail, and 83 percent who use the Internet to research products before buying.

In many cases, consumers are tapping the Internet to learn more about their own doctors' diagnoses or to find scientific data before posing questions to their physicians, said Susannah Fox, director of research at the Pew Project. The Pew Project is a nonprofit, nonpartisan research organization funded by the Pew Charitable Trusts to study the social effect of Americans' Internet use.

"We've heard from people who say they prepare for a doctor's appointment by going online, and then they recover from a doctor's appointment by going online," Fox said. "People are using the Internet to supplement and also to get information they might not have gotten."

Among the most prevalent research topics: specific diseases and treatments, nutrition, exercise, and prescription and over-the-counter drugs.

The drawback to all those inquiries comes when consumers read inaccurate or outdated information online, Fox said.

"The Internet can give you hope. It can validate what you're going through. But it can also make you really anxious," Fox said. "Information is definitely a double-edged sword. But I don't think there are going to be a lot of Internet users who are willing to go back into the dark."

That's true even for consumers whose doctors frown upon independent research or raise concerns about the quality of the information on the Internet, Fox said.

"The lesson here is that people are going ahead and using the Internet, even if their doctor tells them not to," she said. "They just stop telling the doctor where they got the information."

Dr. Barbara Coulter-Smith, a gynecologist at Women's Integrated Healthcare in Grapevine, has firsthand experience with Internet-savvy patients.

She encourages patients to learn about breast-feeding, Pap smears and other medical information online. But she said she points them to specific Web sites and tries to educate them about the importance of credible data.

"We could easily say that 50 to 80 percent of our patients have been on the Internet, and do have questions, and try to even sometimes argue with us," Coulter-Smith said. "It's sometimes just difficult to convince them that anybody can put information on the Internet. They don't have to have any qualifications or credentials."

Still, Internet research can help ease some patients' fears, especially when the findings are in line with their doctor's recommendations, said Dr. Courtney Gibbs, a colleague of Coulter-Smith's.

"At least they come in with valid questions," Gibbs said. "It opens up lines of communication between physicians and patients."

Some health care providers are responding to the growing interest by boosting their own Internet presence.

For example, Baylor Health Care System redesigned its Web site this year to encourage consumer interaction and to tailor information specifically for men, women and senior citizens. Since then, administrators say traffic has risen 50 percent, to several hundred thousand visitors monthly.

Because the Web site's information is vetted by physicians, Baylor hopes that doctors gradually will steer more patients there for reliable information online, said Gail Hartsfield, the hospital chain's director of business development and marketing.

"I think we're going to see more of this specifically, and a lot of this is being driven by consumers themselves," Hartsfield said. "One of the key objectives is to help consumers take control of their own health."

Dr. Martin Weiss, a cardiologist at the University of North Texas Health Science Center in Fort Worth, said the Internet makes it easy for patients to find unconventional medical information.

"It may be alternative medicine, it may be biased advice. And they just don't know that. They just take whatever's on the Internet as truth," Weiss said. "My advice to patients, when I see that, is to find a reputable Web site. A lot of ours will go through americanheart.org. The American College of Cardiology has a very good Web site, too."

Such trustworthy sites actually help doctors, because patients who've done their homework need less time to become educated by physicians, Weiss said.

In fact, the cardiologist raced online himself recently, after he was diagnosed with a rare viral infection that attacks the heart.

"I had questions about what more needed to be done for me. The first place I went was the Internet," Weiss said. "Fortunately, I could weed through all the different listings. There's just a ton of information out there."

The Pew Project study was based on two surveys: a December 2002 telephone survey of more than 2,000 American adults about their Internet habits regarding 16 health topics, and an online questionnaire aimed at collecting anecdotes from almost 2,000 visitors to specific health-related Web sites.

Its findings differed from the conclusions of a report released in March by the Center for Studying Health System Change.

That study found that 38 percent of adults in 2001 had sought health information from any source other than their doctors, and that 1 in 6 turned to the Internet for that information.

Pew researchers attributed the disparity to differing methodologies, noting that their survey didn't limit respondents to any time frame and had a broader scope than the earlier study.

Among the Pew Project's findings:

• Women, who generally are more likely than men to seek health information, also lead the way on the Internet. Eighty-five percent of "wired women" researched at least one of the Pew Project's 16 designated health topics. That compares with 75 percent of men.

• Most Internet users conduct health-related searches just once every few months -- usually on behalf of their spouses, children or someone else. On a typical day, while 49 percent of Internet users tap their e-mail, 6 percent search for medical information.

• Better-educated and higher-income Internet users, as well as veteran Web surfers, are more likely than their poorer, less-educated, less-experienced counterparts to search for health information.

The Internet's popularity as a health resource has swelled since the Pew Project began studying the issue in March 2000. At that time, 54 percent of Internet users reported looking for medical information online.

"If you are, in general, a person of good health, you probably don't have a lot of health concerns that come up," Fox said. "But if you're dealing with a chronic illness or you have a loved one who has a chronic illness, then you're likely to go online every day, every week."