Whereas early studies in network-based language teaching (NBLT) tended to test the technology to see what effects it might have on language use, later studies gradually shifted toward testing theories of second language acquisition within the context of computer-mediated communication. This chapter describes two trends in research on NBLT: one that emphasizes interactionist SLA models and another informed by sociocultural and sociocognitive theories. Most interactionist SLA studies fall into one of three categories: negotiation of meaning studies, transfer studies, or feedback studies. Socioculturally oriented research, on the other hand, has tended to emphasize two main areas: genre differentiation and culture learning in networked classrooms. However, the goals, content, and structure of NBLT are changing rapidly. In contrast to the primarily task- and product-oriented online interactions that characterized early research in NBLT, recent work examines online learning in two new areas: nonclassroom contexts (in which learners’ uses of digital technologies are often more varied and more sophisticated than those they encounter at school) and multimodality (the exploration of semiotic modes beyond text in blogs, wikis, podcasting, mobile phones, bimodal chat rooms, and videoconferencing). As NBLT expands its focus to include cultural, communicative, and social aspects of online teaching and learning, a number of problematic areas arise, such as differences in medium, style, and levels of engagement, technocentrism, and methodological and ethical issues. After describing how researchers are grappling with these issues, the chapter concludes with some thoughts about future directions in NBLT research.