Breast cancer is the leading site of new cancer cases in women. Breast cancer detection is currently primarily based on physical examination by health care professionals, chance findings by women, breast self-examination and mammography used for diagnosis or for routine screening. Early enough detection through mass screening with mammography has been introduced in many countries in the hope that early intervention would lead to reduced mortality and less aggressive treatment. The aim of this publication is to provide an independent, authoritative review of the evidence of the efficacy and effectiveness of breast cancer screening. This will be of value to governments, public health officials and others concerned with policy recommendations for cancer control.