Interethnic and intergroup social ties are critical to knitting together increasingly diverse societies into cohesive wholes. Yet their formation faces the homophily hurdle: important and intimate social ties tend to be established disproportionately between those sharing significant social attributes. In the spirit of analytical sociology, the author explores two mechanisms that could drive intra- and intergroup relations: attraction to similar versus repulsion from dissimilar others. The models differ in predictions as illustrated by data on interethnic marriages in Great Britain and the United States, on U.S. dating and cohabitation relations by religion and education, on educational diversity in marriages in 22 European countries, and on marriages of the native and foreign-born in Austria. A unified model for the two mechanisms, in which tie formation is a conceptualized as a two-stage process of encounter and consummation, is proposed, and its empirical and theoretical analysis provides deeper understanding of the homophily hurdle