This study examines the conditions under which Spanish proficiency is associated with self-esteem among Mexican American adolescents. The study questions the validity of a gross relationship between Spanish proficiency and self-esteem and postulates that the link is stronger: (1) for youth whose significant others prefer speaking Spanish; (2) for youth who speak Spanish with parents and friends, as opposed to only with one group; and (3) for students attending schools with a high proportion of minority students. The study used data from the National Education Longitudinal Study of 1988 to test the interaction effects. Among the results: (1) Spanish proficiency has a significant positive effect on self-esteem for students who frequently speak Spanish with their fathers, but not for those who spoke Spanish with friends; (2) proficiency's positive effect on self-esteem is greater for those who spoke Spanish with both fathers and friends; and (3) Spanish proficiency is related to self-esteem for students attending schools with high minority rates. In conclusion, Spanish proficiency does not seem grossly related to self-esteem. Rather, it positively influences self-esteem only for Mexican American students who frequently speak Spanish with parents and who attend schools with high rates of minority students. The data suggest that the family is more influential than friends in socializing Mexican American adolescents, and may justify differential policies for home-language maintenance or bilingual programs. (TES)