The independent and spontaneous mobilization of social movements during the late 1970s challenged political parties in their very fundamental function of political linkage and has often been deemed a symptom of a crisis of political parties as representative agents. For the first time, it seemed that ‘the political’ extended to other spheres of civil society beyond the traditional party channels. This thesis examines the responses of political parties to social movements in Italy and the Netherlands from the 1970s to the 1980s. Because of their closeness in terms of political identity, social movement scholars have tended to concentrate on the responses of left-wing political parties to social movements. This thesis, which also incorporates this common inquiry, also examines the responses to the social movements of the more distant center-right parties. The major questions that it attempts to answer are: did the observed political parties actually respond to the emergence of social movements? What types of responses did they engage in? What factors explain the variation in the parties’ responses? Each empirical chapter examines the individual party responses to the two most numerically significant social movements that emerged in the Italian and the Dutch national contexts. Drawing on Gamson’s typology of social movements’ success (1975) and on further elaborations of different types of social movements’ ‘impact’, the analysis classifies different party responses by dimension (party discourse and party organization) and type (direct and indirect). Empirical results reveal how, despite the fact that party identity explains variation in the degree to which parties responded to social movements, with parties on the left showing greater responsiveness as compared to center parties, the latter did not remain unaffected by the emergence of social movements. Moreover, results show how also for the case of the leftwing parties, a total adherence to the social movements’ demands did not take place. A two-fold conclusion can be drawn. On the one hand, political parties do channel social movements’ demands, therefore satisfying their function of political representation. On the other hand though, the two worlds of political parties and social movements remain separate, as the inherent constraints of representative government only allow parties to bring forward the social movements’ demands in a mediated form, distant from the movements’ original demands.