The research contained in this thesis involves three interdisciplinary dimensions: Distance Language Education (DLE) as the context of the research, videoconferencing as the technology, and the provision of oral and visual interaction in DLE as the core research problem. Though DLE is increasingly gaining importance at the start of 21st century, the inadequate provision of real-time oral-visual interaction still remains a major deficiency. To be more precise, DLE is still producing language learners who cannot speak the target language. I have outlined the urgency in solving this problem (Wang, 2004a), and it is precisely this urgency that grounds this research. This thesis therefore aims to answer the following central research question: in what ways is oral-visual interaction via videoconferencing able to facilitate L2 acquisition at a distance? In the course of answering the central research question, the following subsidiary questions are closely investigated: 1. What are the needs of distance learners in terms of L2 acquisition? 2. What are the benefits and limitations of videoconferencing-supported oral and visual interaction in the process of L2 acquisition? 3. What are the implications and potential of such interaction for L2 acquisition in distance mode? This thesis is set against a background of research on the importance of interaction in second language (L2) acquisition and the capabilities of Computer Mediated Communication (CMC). Interaction has been regarded as an integral part of communicative language learning, which promotes L2 acquisition (see Gass, 2003; Hall, 1995; Kitade, 2000; Lantolf, 1994; Mitchell & Myles, 1998; Ohta, 1995; Swain & Lapkin,1995). However, the preliminary study in this research established that, in the context of DLE, this interactive dimension has been inadequately provided, and that distance language learners do need an improved platform for L2 acquisition, especially in terms of acquiring speaking skills. The distance factor in distance language education calls for the employment of technology as a medium to provide an interactive platform for oral and visual interaction. Thus, the empirical dimension of this research, involving the participation of both on-campus and distance language learners, witnesses a two-stage evaluation of a particular Internet-based desktop videoconferencing tool, NetMeeting. In this evaluation, NetMeeting was used to conduct videoconferencing sessions, in which the teacher and participants could see and hear each other during the completion of meaning-based tasks. A great deal of original data was collected from the qualitative evaluation in regard to the benefits and limitations of videoconferencing-supported oral and visual interaction in the process of L2 acquisition in distance mode. This evaluation is approached from two aspects: the technological capabilities and pedagogical values of videoconferencing. Recommendations on the use of videoconferencing and videoconferencing task designs are proposed on the basis of the research findings. These recommendations are highly significant for practitioners in this field. Following Murray (1999), a combination of data collection methods was employed in an attempt to effectively explore the scope and depth of the participants' learning experience through videoconferencing. These methods include pre- and post-trial written surveys, in-depth post-session and post-trial interviews, videotaped videoconferencing sessions and the researcher's personal observation. Qualitative data analysis methods were adopted. Particularly important is the use of Varonis and Gass's (1985) model for analysing the negotiation routines during meaning-based task completion. The contributions of this research are manifold. Theoretically, the research updates key definitions in DLE and CMC in keeping with recent developments in each respective field. In so doing, this thesis puts forward a theory of an emerging fourth generation DLE with synchronous oral-visual interaction as its defining feature (Wang & Sun, 2001), and also proposes a new taxonomy in CMC (Wang, 2004). Both theories categorize more precisely the different roles played by different technologies and their implications for different learner goals. Empirically, this research first develops criteria for selecting appropriate videoconferencing tools (Wang & Sun, 2001) and criteria for evaluating the appropriateness of videoconferencing tasks. These two sets of criteria were then applied in the two-stage evaluation of NetMeeting, yielding useful data (Wang, 2004a; Wang, 2004b). This research also contributes to our understanding of videoconferencing task design and performance principles. The significant findings from this research confirm that Internet-based desktop videoconferencing is capable of supporting oral-visual interaction in DLE and leads to significant improvements in L2 acquisition. Most importantly, this study informs future research into the nature of oral-visual interaction enabled by videoconferencing by demonstrating how and in what ways such interaction facilitates L2 acquisition. The rapid development of computer technology makes publishing the contributions of this study an ongoing part of this research, in order to maintain the originality of this study. Some of the findings have been published in top-ranking international journals (see Wang and Sun, 2001; Wang, 2004a; Wang, 2004b). This study addresses a real and urgent need in distance language learning - the provision of oral-visual interaction. Findings from this research shed light on many issues untreated in the literature and in the practices of DLE. They also point to possible future trends in the globalisation of education because the effects of the pedagogical distance between the learner and education provider may be neutralized, or at least, minimized, through the use of CMC.