Data for use in urban analysis and planning research can come from many sources. One particular useful means of obtaining data is through the use of secondary data sources. This chapter introduces the basics of accessing secondary data, with a focus on Australian-based data. It discusses the advantages and disadvantages of using secondary data in research and presents details of a range of potentially useful secondary data sources available in the Australian context. These include data collected in large-scale social surveys together with data that is collected by governments as part of their daily business, including large-scale census collections. The chapter concludes by introducing the area of big data as a useful and exciting form of secondary data.