The results of a national longitudinal survey on the language proficiency of bilingual Hispanic American high school students are reported. Graphs and tables display language proficiency data for sophomores and seniors, language background data by ethnic origin, and family and educational background data by proficiency level. The survey addressed the following questions: language spoken as a child, language currently used at home, family background, relative proficiency in English and Spanish, academic achievement, educational aspirations, and amount of bilingual instruction received. Of the Hispanic students, 40 percent had an entirely English speaking background. Among the remaining 60 percent with a Spanish language background, the findings reveal that (1) Spanish is spoken in most of their homes, (2) they have a lower socioeconomic status than the other groups surveyed, (3) they rank lower on academic achievement and aspirations, (4) the majority of the students do not report themselves to be more proficient in Spanish than English, and (5) the Spanish-dominant students more often received bilingual instruction. (RW)