In January 2000, the Home Office first published local-level crime statistics for the 318 Basic Command Units (BCUs) covering England and Wales. In July 2000, work was carried out to list the 376 Crime and Disorder Reduction Partnership (CDRP) areas in England and Wales in groupings, or families (Leigh et al., 2000). These families were based on socio-economic and demographic factors that were shown to correlate geographically with the level of crime and disorder within a locality. These families were intended to be used: to provide a basis for the national publication of crime statistics at a local level; to help CDRPs identify which partnerships in their family have the lowest crime rates and, over time, are most successful at reducing crime, so that they can learn lessons from them; to help forces and police authorities undertake best value reviews by enabling them to compare local-level performance across a range of functions or processes; and to assist HMIC inspections at BCU level. In July 2000, the Home Office published crime statistics organised by CDRP family (Povey et al., 2000). A need for a similar grouping was identified for BCUs, so that publications of crime statistics at this level could also be organised by family. However, BCU boundaries are chosen according to operational policing needs, and do not necessarily coincide with the CDRP boundaries. Thus, in July 2001, Home Office Briefing Note 4/01, Family Ties: Developing Basic Command Unit Families For Comparative Purposes (Harper et al., 2001) was published, listing the families of the 318 Basic Command Units. A more detailed report is available on the Home Office RDS website www.homeoffice.gov.uk/rds (Harper et al., 2002). A subsequent maintenance of family membership is documented at the Home Office RDS website http://www.homeoffice.gov.uk/rds/pdfs2/basiccommand.pdf (Sheldon et al., 2002). Whilst CDRP boundaries remain unchanged, the BCU boundaries have been changed a number of times since the initial publication of BCU-level crime data organised by family. Some BCU areas were entirely reorganised, usually resulting in a reduction in the number of BCUs, with several smaller areas being rearranged into a smaller number of larger BCUs. Such changes have occurred a number of times – the most recent taking effect from 1 April 2003, those prior to that taking place on 1 April 2002. The overall objective of this work, then, is to update boundaries, socio-economic data and family membership of the BCUs in the light of changed boundaries.