Through ignorance, bank exclusion is often taken to be a mere consequence of social exclusion. The main measures that propose to limit the problem (the right to an account, the procedure for individual insolvency) therefore address the visible effects rather than the causes. The purpose of this article is to deal with the problem in terms of its causes as well as its consequences. Bank exclusion derives from the difficulties encountered by banks and some of their customers in establishing a banking relationship that makes joint production of the service possible. Customers in unstable circumstances or with limited banking knowledge have specific needs which often conflict with trends in the banking sector, which are in the direction of automatisation and industrialisation of the most basic banking services. The difficulties of access and use that follow from this discrepancy are particularly damaging for such customers because banking services now have a central place within modern societies. Exclusion from banking thus contributes to the more general process of social exclusion.