People with a strong family history of certain diseases, such as breast, colon, or prostate cancer, should generally be tested for the ailment earlier and more often.

And certain treatments--such as high-dose antioxidant supplements to prevent blindness from macular degeneration--may be worthwhile only if the disease runs in your family.

What to do: Create a medical family tree, noting especially your relatives' dates of birth and death and any major diseases they've had. (Consider using the tool developed by the National Institutes of Health, at www.familyhistory.hhs.gov.)

Then discuss it carefully with your doctor at your next checkup.