The literature on screening mammography includes a plethora of conflic
ting articles. More recently, individuals and various medical organiza
tions have recommended and established their own guidelines for screen
ing mammography. A review of salient breast screening randomized clini
cal trials in women over and under the age of 50 years is provided and
compared with the more recent results of the Canadian National Breast
Screening Study. In women under the age of 50 years, screening mammog
raphy cannot be supported from the results of these trials. In women o
ver the age of 50 years, screening mammography leads to a significant
reduction in breast cancer mortality and should be strongly recommende
d.