- MAMMOGRAM: Most women don't need a mammogram in their 40s and they should get one every two years starting at 50, according to the U.S. Preventive Services Task Force, a government-appointed but independent panel.

The task force says screening earlier and more frequently often leads to too many false alarms and unneeded biopsies without substantially improving women's odds of survival. Their advice is controversial and other national guidelines recommend that screening start at 40.

Screening with a pap smear shouldn't start until age 21. The group cited studies showing no increased risk of cancer for women in their 20s if they extended screening to every two years. Other national guidelines vary slightly.

- PROSTATE CANCER: While many men get tested, most groups don't support routine screening for prostate cancer. The American Cancer Society says doctors should have a frank discussion of the benefits and limitations at age 50 with men at average risk. In a recent update, the group says if a man wants to be screened, the PSA blood test should be given, but a digital rectal exam is optional. The American Urological Association no longer supports annual tests but suggests a baseline PSA test at 40, with follow-ups based on each man's situation.

- HEART TESTS: A recent study suggests too many low-risk patients are given angiograms to check for heart disease. The researchers say doctors could do a better job of choosing who really needs the exam. The test carries a small but real risk of causing a stroke or heart attack, and also involves radiation exposure.