In France, breast cancer is the most common cancer among women; in 2000, it accounted for 35.7% of all new cancer cases and 20.2% of cancer deaths among women. The organized breast cancer screening program has been available nationwide since 2004. It targets women aged 50 to 74, offering them a free mammogram every two years with a second reading in the event of a negative result. An evaluation of the organized breast cancer screening program in 2005 showed a participation rate of 45%, below the 70% rate recommended at the European level. The mammography coverage rate estimated by the 2005 Cancer Barometer of the National Institute for Prevention and Health Education was approximately 70%. The share of individual screening (IS) in mammography coverage appears to be close to 15–20%. Insufficient participation by women in the organized screening program results in a decrease in the expected effectiveness of screening on mortality. Furthermore, women’s use of IS has implications for the program’s cost-effectiveness. The objective of the study on factors influencing participation in organized screening (FADO) was to analyze the characteristics—both sociodemographic and related to access to care—associated with participation or non-participation in organized screening as well as in individual screening, in order to better target awareness-raising efforts among women and healthcare professionals. (R.A.)