Our proposed research focuses on the interplay between pro- and anti-immigrant movements in Italy and Spain. We attempt to fill a gap in the social movement literature by analyzing the processes and mechanisms by which social movements affect each other. A systematic study will be provided that will shed light on various aspects of the mobilization-countermobilization (MCM) impact. In particular, we will examine how each side affects the forms, development, claims, and efficacy of its opponent, the conditions that allow certain consequences and the processes leading movements to have an impact on each other. The project focuses on three key aspects of the interaction between pro- and anti-immigrant movements. First, we investigate how framing strategies evolve according to the needs of SMOs (social movement organizations) embroiled in MCM-generated conflicts. Second, we examine the ways in which MCM dynamics influence a movement's selection of particular tactics. Thirdly, we scrutinize how the dynamics of movement-countermovement interactions are influencing the construction of activists’ collective identities. The primary aim of the research is to advance our understanding of the polarization of the politics of immigration through the examination of relevant social movement interactions. In order to reach this goal our research project aims to develop a closer connection between migration and social movement research.