It is well established that mammographic screening helps reduce mortality from breast cancer in women aged 50 to 69 years. Since 1998 Québec’s breast-cancer screening program, the Programme québécois de dépistage du cancer du sein (PQDCS), has offered screening to all women in this age group through a screening test every two years. Recent evidence indicates that annual screening for women aged 40 to 49 years may be effective in reducing mortality from breast cancer, although less so than for women aged 50 to 69 years. In that context, AETMIS was asked to examine the possibility of offering women the opportunity to take part in a systematic mammographic screening program starting at the age of 40.