This paper examines social and economic mobility in the Crown of Aragon in the long term. It is divided into three main sections. The first deals with the processes of social mobility linked to both the colonisation of territories taken from the Muslims in the 12th and 13th centuries and the impact of the Black Death and other calamities in the second half of the 14th century. The second section addres¬ses both the shorter-range migrations, especially from the countryside to the city, and the dynamics of social mobility in rural world and urban society. Although related to the latter, we wanted to highlight, as a separate section, the case of the converts from Judaism, as an original and important phenomenon both quantitatively and qualitatively, and for both its success and failure, in the Crown of Aragon and the other Iberian states. Finally, the third section is devoted to some questions of approach and methodology, in particular political (from the lists of families who held public offices in certain cities) and economic (from tax records or wealth registers) ones.