Spain has recently become the destination for large numbers of international migrants and now ranks as a key focal point for international migration in Europe. Currently, approximately one in ten residents in Spain are foreigners, up more than tenfold from figures holding at the outset of this century. Migration has now become a major social and political issue in the country. In order to provide reliable data about migrants in Spain for researchers and policy makers, acting on a proposal of a research team working within the context of the Population and Society Research Network (GEPS), the Spanish Statistical Office has recently carried out an extremely ambitious survey of foreign-born persons currently living in Spain. In the course of the survey, nearly 15,500 persons were interviewed regarding a large array of issues pertaining to their migration experience. Important documentation, including the project report, the methodological specifications of the survey, and the anonymized micro data have recently been made available to the scientific community and to policy makers at the website of the Instituto Nacional de Estadística. The purpose of this paper is to describe this data source, its content, its methodological underpinnings, and the way the fieldwork and data cleaning were carried out. Examples of preliminary results will be presented so as to underscore the potential this survey affords for researchers everywhere.