In this chapter we present key concepts relating to geographically referenced data in social science research.  We describe how such data are collected, how they can be found online, mapped and analysed.  We explain the role of geographical information systems (GIS), and guide readers who wish to find out more about GIS to relevant introductory sources. Our discussion of the emergence of online tools for geographical data is subdivided into: Data sources (e.g. Neighbourhood Statistics Service, American Factfinder); Geographical linkage (directories, lookups, e.g. GeoConvert); Mapping (both online, using virtual globes and mapping sites, and offline using data from the Internet); and more specialist spatial analysis tools.