This chapter begins by conceptualizing what the social integration of migrants entails. The discussion focuses upon two social structural dimensions: socioeconomic status, primarily indicated by education, and spatial integration/segregation, typically measured by the Index of Dissimilarity. The cultural dimension of integration is examined in relation to intermarriage, and race, gender and educational levels are examined as potential constraints upon people's choices in marriage markets. Assimilability is discussed as a criterion for migrants’ admission but viewed as over-simplified because it does not recognize the degree to which migrants can integrate in a destination nation without severing ties back in their origin nation.