A study of the interrelationships of linguistic and communicative competence in English and Spanish, self-concept, field-independent cognitive style, and scholastic achievement among Mexican-American pupils at the elementary, junior high, and high school levels found that linguistic and communicative competence were highly related within languages, and communicative abilities were also related across languages. Language dominance varied considerably, depending on whether linguistic or communicative tests were used, with linguistic measures increasing Spanish dominance and communicative tests favoring English dominance. Field independence was found strongly related to all measures except Spanish linguistic competence, with the latter having an expected negative relationship to length of United States residence. Self-concept was strongly related to language tests and academic achievement. English language proficiency, achievement, self-concept, and field independence increased with length of U.S. residence and seemed related to acculturation. English linguistic and communicative competence tests related strongly to global English competence evaluation and quantitative measures of language quality in speech samples. Both communicative and linguistic competence measures are recommended for making educational decisions, as well as research on the relationship of motivation types to achievement and special characteristics of students who adapt well to the U.S. (MSE)