This paper describes a prototype software tool for support of peer-to-peer conversation in distance education courses in text-based asynchronous mode, utilizing the visual structure of multiple threads of conversation. The theoretical basis for this design is a comparative analysis of oral, written, and electronic communication that enables the identification of properties of the conversation structure relevant to software design--fragment length and fragment linking mode. Combination of these properties gives rise to linear or multithreaded conversation structures. Topics discussed include: (1) conversation, including conversation structure and linearity, conversation fragment linking, and stylistic aspects of oral, written, and electronic conversation; (2) existing systems that support text-based conversation, including e-mail and conferences, the Coordinator tool, hypertext systems, and electronic whiteboards; (3) the prototype, including its main properties and implementation; and (4) conclusions and future research plans. A table contains a comparison of oral, electronic, and written media. Two figures illustrate an e-mail transcript and conversation threads represented spatially. (Contains 25 references.) (Author/DLS)