Many Western European countries have seen strong debates about minority rights and practices such as the founding of religious schools or the wearing of religious symbols in public institutions. In these increasingly diverse societies, tolerance of one another’s practices and beliefs has often been put forward as an indispensable ingredient for harmonious intergroup coexistence. The classical notion of tolerance entails the acceptance of practices that one disapproves of – which implies that tolerance is a balance between reasons to accept and reasons to reject disapproved practices. In this dissertation, Evi Velthuis investigates those reasons for, and boundaries to, intergroup tolerance. Using large-scale surveys and experiments from the Netherlands and Germany, this dissertation presents four empirical chapters which consider three main aspects of tolerance: (1) reasons why minority practices are tolerated, (2) situational factors when practices are tolerated, and (3) individual differences in who tolerates minority practices. The findings and contributions are discussed in light of the social scientific literature on tolerance and intergroup relations.