The Internet can be a valuable medical tool, helping many patients learn about symptoms and treatments.
According to one survey, 80 percent of Internet users in the United States have searched the web for medical or health information.
The problem is, much of the medical information on the Internet is dangerously incomplete or flat out wrong.
Here are some Web sites that doctors told ABC News are good sources of information:
Cancer.gov -- the official site for The National Cancer Institute.
Familydoctor.org -- operated by the American Academy of Family Physicians.
Healthfinder -- health information from government agencies, and partner organizations.
HIV InSite is a project of the University of California San Francisco AIDS Research Institute.
Kidshealth -- health information about children from before birth through adolescence.
MayoClinic -- health education for patients and the general public.
Medem -- a project of the American Medical Association, the American Academy of Pediatrics, and the American College of Obstetricians and Gynecologists.
MEDLINEplus -- a consumer-oriented site by the National Library of Medicine,