Understanding the nature and process of change over time is an important part of social research. Large-scale longitudinal studies, such as the various birth cohorts and the British Household Panel Survey, have transformed the way in which we understand the relationships between individual lifecourse, family formation and dissolution, economic and social change, and social policy. Qualitative methods for longitudinal research are not yet as well established in social policy research as quantitative methods, but they are attracting increasing interest. The papers in this themed section were first presented at a Social Policy Association sponsored workshop held in London in November 2005. The main aim of the workshop was to explore the challenges of using such data for policy-related research, focusing in particular on data analysis and interpretation.