Stein Rokkan became one of the central figures of European comparative politics and political sociology in the post-war decades. He wrote numerous papers, articles, and chapters, but Citizens, Elections, Parties, was his only single-authored book. CEP remains the most complete guide to Rokkan's work up to 1970, and it is for this that Rokkan is most widely known today. The core question at the heart of this seminal work is what explains the political behaviour of citizens. The book brings together a series of studies, some conceptual and theoretical, others empirical and statistical, of processes of political development in industrialising and industrialised societies. The fourteen studies presented in the volume focus on three central themes in the comparative sociology of national development: first, the extension of citizenship to hitherto underprivileged strata of each territorial population; second, the mobilisation of the new masses through the institutionalisation of elections and the formation of parties and popular movements; and third, the reactions of the mobilised masses to the alternatives presented to them by the inherited national regime, by the parties, and by the new media of communication. Rokkan's work, as represented in Citizens, Elections, Parties, remains alive today; his analysis of the structural underpinnings of citizen behaviour was innovative and highly ambitious in its day and still remains relevant, with many of the questions he raised still not receiving an adequate answer.