(FORTUNE Magazine) – As amazing as the quality of medical care is in this country, our health system is still far from perfect. Way too many people throw money at unproven treatments; others lack access to essential medical services. According to one estimate, more than 50,000 people die needlessly every year because they don't receive appropriate preventive care.

That is why it's essential to take matters into your own hands. Doing your own medical homework is not only crucial to making sure you get the proper treatment, but it can also save you a bundle. Hospitalizations resulting from avoidable second heart attacks, for example, are estimated to cost the nation more than $1 billion a year.

The Internet can help. The Mayo Clinic (www.mayoclinic.com) offers several online Health Decision Guides to assist you in making the best treatment decisions for everything from knee injuries to herniated disks. A site created by the partnership between the Foundation for Informed Medical Decision Making and Health Dialog (www.collaborativecare.net) provides videotapes examining options for prostate and breast cancer, as well as other common ailments. At NexCura (www.nexcura.com) the company's search tool will call up peer-reviewed clinical studies relevant to your condition after you fill out a detailed questionnaire about your diagnosis.

Finally, the big disease-prevention organizations such as the American Cancer Society (800-ACS-2345) and the National Kidney Foundation (www.kidney.org) offer free screenings around the country. The best way to cut your health-care expenses, after all, is to stay out of the doctor's office in the first place. --D.S.