This research study focuses on two interrelated aspects of the development of bilingualism, the development of awareness of two separate linguistic systems and the occurence of interference phenomena. The research was conducted in a small town in East Central Illinois. The sample for the study included all the Mexican-American children enrolled in kindergarten through the fourth grade and three preschool children. The primary sources of data were tape recordings of natural discourse. The study is divided into the following chapters: (1) Introduction; (2) Deviations from Standard English and Spanish; (3) An Evaluation of the Spanish and English Deviations from Standard Language Norms; (4) The Acquisition and Use of Spanish and English Color Terms; (5) Special Functions of Code-Switching; (6) Stylistic Code-Switching in Narratives; (7) Bilingual Strategies of Communication; (8) Intra-Sentential Code-Switching; (9) Language of the Sentence; (10) Ellipsis in Bilingual Discourse; (11) Developmental Trends in the Syntax of Code-Switching; and (12) Conclusion. An appendix provides demographic information on the population studied and references. (CFM)