This paper focuses on an important aspect of second language acquisition, namely, the complex set of modifications in the rules governing the forms and functions of the new language that are required by specific sociocultural contexts. These adjustments in language, or shifts in register, play a crucial role in interpreting utterances for social meaning, and are a major component of communicative competence, defined here as sociolinguistic competence. Specifically, this paper examines the shifts in register that occur in the development of interlanguages by second language learners, analyzing a set of syntactic-semantic modifications in language use, and contrasting student/teacher with student/student discourse. Special attention is given to the following questions: at what point in second language acquisition does the learner demonstrate sensitivity to the sociocultural rules that govern the teacher's language? Is the learner more sensitive to the norms emerging from student/teacher relationship or to those in student/student discourse? And finally, what speech acts conform to teacher's language norms earlier than others? (MES)