Research was conducted to examine the language acquisition of a Mexican-American child who has been brought up in a linguistic environment where code-switching between Spanish and English is the dominant style of speaking. In addition, the relation of code- switching to the acquisition of bilingualism is analyzed. The speech of the subject, a two-year-old boy in a middle class bilingual family, was recorded and analyzed for nine months. Observations concerning the child's speech habits and linguistic repertoire were also considered in the analysis. Documentation is provided on the structure and rules of code-switching. It is concluded that code-switching appears not to be detrimental to the development of bilingualism, but, on the contrary, seems to be one approach to the simultaneous acquisition and maintenance of two languages. (AMH)