Changes in adolescents' ethnic identity (e.g., exploration, belonging) were examined over the 4 years of high school. Results from 541 adolescents (51% female) with Latin American, Asian, and European backgrounds suggest that, as a group, adolescents do not report developmental changes in their ethnic exploration and belonging over time. Yet, within-person analyses of change reveal that individual adolescents exhibited substantial fluctuation in ethnic identity across the years, and this fluctuation was associated with concurrent changes in family cohesion, proportion of same-ethnic peers, and ethnic centrality. The discussion focuses on the value of examining intraindividual change over at least several years in order to more fully understand processes of ethnic identity development during adolescence.