This chapter introduces the participation measures in the International Social Science Program (ISSP). Citizens in roughly a dozen and a half affluent democracies were survey in 2004 and 2014. Analyses identify five modes of participation: voting, contributing funds, contacting political figures, protest, and online participation. These modes are compared in terms of their characteristics relevant to inequality of participation, such as the skills and resources required to be active. The chapter presents the levels of political activity in each mode across established democracies in 2004 and 2014.