For more than four decades the analysis of party organizations in the European democracies has been completely separated from analyses of American party structures. The first part of this article examines how and why such a separation was to emerge in the aftermath of Duverger's and Epstein's path-breaking original work. It then goes on to outline how an analytic framework might be developed so that more wide-ranging comparative studies of party organizations in democratic regimes can be undertaken in future. Only with such research can the limitations of ‘exceptionalist’ and ‘regionalist’ explanations of party structure development and change be overcome.