Distinguishing between interethnic and interracial coupling offers new understandings about family diversity, as well as the assimilation of immigrants and their children. An analysis of the Children of Immigrants Longitudinal Study, a survey (N = 1,480) of the children of Asian and Latin American immigrants who live in Southern California, finds that a more accurate conceptualization of mixed couples should distinguish between interethnic and interracial couples. Although race remains a significant boundary in relationship formation, ethnicity is also important, especially in terms of language and religion. This study has demonstrated that race and ethnicity are both important social boundaries for understanding mixed couples and denote different types of mixed couple--interethnic versus interracial couples--and different types of lived experiences. At the very least, this analysis of mixed couples calls for the inclusion of interethnic couples within studies of intermarriage. (Contains 7 notes, 2 tables, and 3 figures.)