The addition of 2001 Census data to the ONS Longitudinal Study extends the range of research topics that this unique data resource can support. Census questions on religion, care-giving and self-rated health that were asked for the first time in 2001 and the repetition of 1991 questions on limiting long-standing illness and ethnicity raise opportunities for new longitudinal investigation in these areas. This article describes how new 2001 methodologies including data imputation, the One Number Census and de jure enumeration affect the LS database. The support service for existing and prospective LS users is described.