Indiana University-Purdue University Indianapolis (IUPUI) / The study of L1 and L2 uses by graduate students in a genuine immersion context or study abroad has not been widely explored. This study is an attempt to provide new insights from the perspective of the interactional and sociocultural sociolinguistics while maintaining constant links with studies in Second Language Acquisition and study abroad. The data collection stage of this study took place at the Universidad de Salamanca in Spain during the summer of 2005. For data collection, the researcher used participant observation. Students also completed a questionnaire about their uses of L1 and L2 while in their home country and during their stay in Spain, one at the beginning and another by the end of their studies in Salamanca. Results first concluded that the uses of L1 seem to be linked to the students’ own effort to carry out their class work or to learn more about the language or the topic they are working on in class, without being directly related with their instructor’s primary objective. Similar uses have been reported by Antón & DiCamilla (1999), Alley (2005), Brooks & Donato (1994), and Centeno-Cortés & Jiménez (2004). Secondly, perceived uses of L2 in the classroom were mostly related with those reported by Tarone & Swain (1995), that is, students used L2 for academic purposes. Thirdly, the L1-L2 switching supported by the findings of Liebscher y Dailey-O’Cain (2005) seems to indicate that students perceive themselves as a bilingual speech community and take it for granted that their interlocutor is proficient in both languages. Finally, the study suggests some pathway for future research including the reasons for the poor L2 use by students whose supposed proficiency level is advanced as reported in the study. Additionally, some pedagogical implications are provided.