The present project is an analysis of code-switching between English and Spanish or Catalan in three different groups of subjects: six adults from the bilingual community of Gibraltar, six children acquiring two languages simultaneously and six adults acquiring a second language. The main objectives proposed are to determine whether the syntactic constraints for code-switching apply to the three groups in question, to understand how and when syntactic restrictions on code-switching are acquired, and to analyze the social and pragmatic functions of code-switching in each one of the groups cited. In summary, two important goals set for this project consist in examining the revelance of age in the process of acquisition of code-switching as well as the role of a speaker's linguistic competence.