Computer-mediated communication (CMC) is used in different contexts and uses different tools, such as those of computer conferencing, e-mail, and groupware. This article introduces the use of Formal Concept Analysis (FCA) as a methodology to visualize the data in CMC. FCA, which is based on a mathematical lattice theory, offers visual maps (graphs) with conceptual hierarchies. Combined with content analysis, FCA is proposed as a potential method for the analysis of CMC. In this study, three categories (social, cognitive, and metacognitive) from F. Henri's (1992) model for CMC content analysis were applied to FCA after a previous study used a content-analysis method based on Henri's model to convert data from a computer conference. On-line discussions (computer conferences) in an applied educational psychology course were analyzed. The conferencing messages were converted by the content analysis and then scaled into single-values attributes to compile a lattice. This article provides an example of the application of FCA to CMC and shows its potential for analyzing on-line discourse. (Contains 3 tables, 13 figures, and 31 references.) (SLD)