Background. While low participation in breast cancer screening is associated with lower individual socioeconomic status, the reasons for this insufficient participation are not fully understood. Our objective was to analyze the influence of the socioeconomic environment and healthcare provision on participation in organized breast cancer screening among a representative sample of the target population in the Calvados department. Methods. The sample included 4,865 women aged 50 to 74 selected at random from the target population of Calvados between 2004 and 2006 (n=98,822). Individual participation data and aggregated socioeconomic data, derived respectively from the organization responsible for organized screening and the population census, were analyzed simultaneously using a multilevel model. Results. Participation was lower among the youngest (50–54 years) and oldest (70–74 years) women compared to those aged 55–69 years, with OR=0.73 [95% CI: 0.64–0.83] and OR=0.78 [95% CI: 0.67–0.91], respectively. In the most disadvantaged geographic areas, the probability of participating was 29% lower compared to advantaged areas (ORa = 0.71; 95% CI: 0.59–0.86). No significant influence of the presence of general practitioners or certified radiologists was found. Conclusion. Social inequalities in screening could be reduced through targeted interventions aimed at populations at risk of low participation, identified by multilevel analyses incorporating individual variables and an ecological deprivation index specific to the French context. (R.A.)