The use of computer technology in English language teaching and learning is accepted, often uncritically, in many settings, even though in other settings, computers are not available, while in still other settings, teachers and learners often lack the necessary computer literacy skills to exploit the technology effectively for language learning and teaching. While many articles and books discuss tips for using computer-bases technologies in the classroom, research studies tend to be small scale and seldom generalizable. Still lacking is a rigorous approach to the study of the implementation of computer-based technologies (both how the technologies are implemented and which technologies are chosen); the effects of computer-based technologies on instruction (including effects on the role of the teacher); the effects of computer-assisted instruction on language learning; and the integration of computer-assisted instruction into curriculum design. This chapter summarizes extant research in these areas, while identifying the assumptions underlying much of the literature on the use of new technologies. The chapter also predicts, from the existing research data, what would be necessary for computers to be ubiquitous and part of teachers’ repertoire of instructional approaches.