This article describes the scope and composition of national associational populations in four similar countries (Australia, Canada, the United Kingdom, and United States), by way of introducing an important new data release on national associational populations. Special attention is devoted to the subset of associations attending to social inequality issues of gender, race/ethnicity, and sexual orientation, and which are of particular interest to social movement and interest group scholars. No evidence is found for the Tocquevillian notion of heightened national-level associational activity in the United States. The nonmembership associational form is, however, particularly prominent in the United States. Associations attending to social inequality issues in the United Kingdom are structured very differently from these other nations, likely as a result of the unitary nature of government in that country rather than a strong federal system.