This study examines the relationship between proficient bilingualism or biliteracy (proficiency in reading and writing in both Spanish and English) and the self-esteem of Mexican American students. The concept of proficient bilingualism has not been widely used to examine bilingual education's noncognitive functions, in particular its effect on the self-esteem of Mexican American students. This study analyzed data from the 1988 National Education Longitudinal Survey. The sample included 1,034 Mexican, Mexican American, and Chicano eighth graders with a Spanish-English bilingual background. Based on self-report, students were categorized as either biliterate, English monoliterate, Spanish monoliterate, or oral bilingual. A set of 13 questions that measured self-esteem were factor analyzed, generating three subdimensions (self-deprecation, self-confidence, and fatalism). Controlling for students' sociodemographic background, school experience, academic performance, and status among peers, analysis revealed: (1) Mexican American children who saw themselves as biliterates had the highest self-confidence as compared to monoliterates and oral bilinguals; (2) English monoliterate children had lower fatalistic attitudes than other children; (3) self-reported Spanish monoliterates seemed disadvantaged in the three measures of self esteem; and (4) there was a strong interactive effect between parents' education and children's birth place (U.S. or foreign) on biliteracy identity. This paper includes data tables. Contains 40 references. (LP)