Many studies based on the Office for National Statistics Longitudinal Study (ONS-LS) have focussed on socio-economic variations in demographic events. For example, the ONS-LS has been the basis of much influential research on inequalities in mortality, and in health status, and has been used to analyse socio-economic variations in fertility and in migration as well. This guide will help you to choose appropriate socio-economic indicators from the ONS-LS for your research question, combine individual, household and area level indicators to their best effect and formulate a request for such data.