Synchronous computer-mediated communication (CMC), more commonly known in the Internet world as "chatting," has become an increasingly popular way to communicate for a variety of purposes. While CMC is still primarily recreational in character, educators are waking up to the possibilities of harnessing this activity for pedagogical purposes. The purpose of this study is to investigate the interactional and linguistic features of communication among intermediate level Spanish learners and their teacher in a synchronous CMC context. The study evoked some of the fundamental constructs of Vygotskian sociocultural theory in order to describe and explain how learners and their teacher collaborated with each other to co-construct meaning in chat rooms. General patterns of learner-learner and learner-teacher interaction were analyzed, as well as learner and teacher perceptions of the use of chat as a language learning tool, and finally, changes in learner output over time. The study found the following: (1) learners appropriated the chat room environment to create their own community of language practice in which they significantly influenced the tasks assigned to them; (2) learners and teacher had a variety of perceptions regarding the use of chat rooms in a second language learning class, which brought an "emic" perspective to the study; and (3) the Spanish verbal morphology system served as a springboard for illustration and discussion of changes over time. (Contains 106 references.) (KFT)