[Abstract] OBJECTIVES - to explore the patterns and determinants of reattendance among initial attendees at an organised breast cancer screening programme. SETTING - Swiss mammography screening pilot programme, based on first-round enrolment in 1993-1995. METHODS. Data on sociodemographic features, health preventive behaviour and history, prior screening round and referring physicians' attributes were collected at initial attendance. First-round attendees (n=4'162) were followed prospectively through next screening round. Determinants of reattendance were identified by multivariate logistic regression. RESULTS - Reattendance rate was high (80%). Women most likely to reattend were urban, Swiss residents with a true-negative first-round screening result. The more intensive the initial recruitment efforts, the lesser were the odds of reattendance. Mammography screening prior to screening enrolment increased reattendance. Having a gynaecologist, a female and a younger doctor as a referring physician was positively associated with reattendance. CONCLUSION - Mammography screening attendance is not only influenced by women-related factors but also by structural factors, and thus requires a global approach. For strategies aimed at improving performances of organised cancer screening programmes, understanding and quantification of determinants of (re)attendance are key elements to consider. [Authors]