Attachment is a long-term emotional link between infants and their mothers. Attachment quality influences subsequent psychosocial relationships, the ability to manage stress and, consequently, later mental health. Home intervention programmes targeting infant attachment have been implemented in several contexts with varying degrees of efficacy. Within the CAPEDP study (Parental Skills and Attachment in Early Childhood: reduction of risks linked to mental health problems and promotion of resilience), a subsample of 120 families were recruited with the objective of assessing the impact of this home-visiting programme on infant attachment organisation using the Strange Situation Procedure. The present paper describes the methodology used in this ancillary study.[résumé auteur]