An important question for the acculturation of adolescents from immigrant families is whether they retain ethnic labels that refer to their national origin (e.g., Mexican, Chinese) or adopt labels that are dominant in American society (e.g., Latino, Asian American, American). Approximately 380 adolescents from Asian and Latin American immigrant families selected ethnic labels during each of the 4 years of high school (age span = 14.87-17.82 years). Results indicated no normative trend either toward or away from identifying most closely with pan-ethnic or American ethnic labels. Significant numbers of adolescents changed their ethnic labels from year to year, however and these changes were associated with fluctuations in adolescents' ethnic affirmation and exploration and proficiency in their heritage languages.