Who participates in demonstrations? Analyses of participants have emphasized the role of political disaffection, strategic resources, and context. Against the backdrop of the rise of protest politics in both older and newer democracies, this article addresses the question by focusing on Belgium, a postindustrial society that exemplifies changes in protest politics and can be studied through detailed surveys of participants in demonstrations. Demonstrators are similar to the Belgian population in general. There is little evidence that they are antistate radicals. Yet some significant social, attitudinal, and behavioral contrasts demarcate different groups of demonstrators. Far from threatening the state, demonstrations have become a major channel of public participation in democracies.