This paper provides an introduction to the practice of community-led enumerations as conducted by Shack/Slum Dwellers International (SDI). It sets out the historical context for enumerations, which came out of a need in India in 1975 to find a more long-term solution to evictions, and charts its subsequent evolution and spread throughout other countries. Enumerations can help to build a community, define a collective identity, facilitate development priority setting and provide a basis for engagement between communities and government on planning and development. This process allows communities of the urban poor to assert their rights to the city, to secure tenure, livelihoods and adequate infrastructure. The paper discusses some of the specific methodological issues, including the challenges of legitimizing community data, and the use of technology by slum(1) or shack dweller federations when appropriate.