For people who want to take at least partial control of their own medical conditions, the Internet seems like a gift.

Imagine - more than 250,000 Web sites that deal directly with health issues. And that doesn't include newsgroups.It's no wonder that 15.6 million adults surfed the Web for medical information last year - nearly 43 percent of all Internet users, according to the Associated Press.

But while some of them got valid information, a lot of them probably got stung. There's too much information out there, according to the Internet Health-care Coalition. And nobody's screening it.

Consider this: A simple search for information on heart attacks yields 1.15 million links. Plug stroke in as a keyword and you'll find more than 3,000 Web sites. Fortunately, adding the word treatment cuts the list to 65 - at least manageable. But it still doesn't tell you if you'll find good information or serious quackery.

The Health on the Net Foundation, which is based in Europe, offers tips on its Web site to help people differentiate between legitimate medical information and tomfoolery.

The first step is to be skeptical. But sorting out what's accurate from what's not in a field as complex as medicine depends more than anything else on the reliability of the source.

And word of mouth - or in this case, hypertext links from one reliable source to another - do a lot to vouch for a site.

The U.S. Department of Health and Human Services official medical Web site provides a wealth of information on health and related topics, including links to at least two dozen sites it considers re-li-able.

Healthfinder, located at (http://www.healthfinder.gov/) breaks itself down into prevention and self-care issues, choosing quality care, online health information, fraud and complaints, Web resources, organizations (like the American Medical Association), hospital accreditations, choosing a health plan and more.

The Healthfinder "Just for You" pages offer top picks and the best wellness and health information by age group and ethnicity. There are also full search capabilities throughout the site.

Perhaps the most valuable information on the site, for those trying to research symptoms and treatments of a specific condition, are 35 core subjects that have produced the highest volume of usage: topics like cancer, diabetes, heart disease, nutrition, immunizations and more.

Healthfinder also offers a fine selection of libraries, online journals, medical dictionaries and other resources.

Intermountain Health Care operates a Web site that has only increased in popularity with time, according to IHC spokesman Jess Gomez.

The site, Http://www.ihc.

com/, has four special sections. One lists job openings at all IHC facilities. Another provides information on IHC facilities in different areas. Still another looks at background information on the IHC Health plans and includes a request form for more information.

But the most popular feature - one that is often used by doctors in other areas, according to Gomez - is a look at "cutting-edge research performed at IHC hospitals."

That includes information on surgeries, recent publication of work done by IHC employees in different medical specialties and departmental research and special topics. The site also lists current clinical trials that are occurring at different IHC facilities.

Dozens of medical schools operate legitimate Web sites. So do nationally recognized and trusted organizations associated with specific conditions or diseases, like the National Arthritis Foundation, or with professional groups, like the American Medical Association.

But medical experts and Internet watchers agree that a trip to the Web was never intended to replace a check-up by a physician.

It's just a tool. And how effective a tool it is depends, of course, on the skill of the one who wields it.