Social identities, conceptualized as self-designations and measured by the TST, were examined for samples of high school adolescents in three societies: the United States, Puerto Rico, and Mexico. Four identities were explored in terms of salience, frequency, and valence: gender, religion, family, and peer. For both males and females in Latin and Anglo cultures gender emerged as the most prominent identity. Religious IDs were more frequent for Catholic adolescents. The strongest cultural difference was found with respect to negative religious IDs: these were significantly more frequent for Anglo adolescents. Positive gender and family IDs were more frequent for Latin adolescents, while peer IDs were slightly more common self-designations for Anglos. These tendencies were generally in the expected direction. Social and cultural differences between these Anglo and Latin societies were considered as explanations for variations in adolescent identity structures.