In 2003, INSEE conducted the Life History survey on identity construction, with the aim of analysing present-day forms of social integration through description of the social tie, both real and symbolic, constructed in individual histories and collective affiliations. The article presents the conceptual foundations of a project that has its rationale in the context of recent structural modifications, notably those affecting two key institutions and traditional sites of integration, work and the family, but also relationships with free time, new forms of involvement, geographical mobility, etc. The authors relate the different stages in the survey design. A preliminary qualitative study was used, first, to catalogue the different forms of identity definition—status-based, psychological, narrative—that respondents use to define themselves, and second, to show the diversity of the themes of identification, the meaning and values attached to them, and the ways in which people link them together to construct their identity. This qualitative phase guided the development of an open-ended questionnaire that combined retrospective biographical data with objective and more subjective data pertaining to the various social affiliations—affiliations that may be de facto, appropriated or at times imposed.