Journal article: Homophily—the tendency individuals have to associate with similar-others—is a powerful determinant of social networks. Yet research to date does not allow us to determine which dimension, e.g., ethnic, religious, gender, age, or class similarity, drives association. Tests demonstrating homophily are flawed by restricting the range of dimensions in the choice set. We introduce an experimental game in which we exogenously expose subjects to diverse partners to determine which dimension dominates. We find that in a socio-demographically diverse district of Paris, despite expectations of secularization, religious similarity significantly predicts homophily. Moreover, we provide tentative evidence that religious homophily is taste-based.