Genre analysis, the investigation of typified communicative actions arising in recurrent situations, has been developed to study information use and interchange online, in businesses and in other organizations. As such, it holds out promise for the investigation of similarly typified communicative actions and situations in CSCL contexts. This study explores this promise, beginning with an overview of ways that genre analysis has been adapted and applied in related areas: in the study of group behavior in organizations, and of evolving and proliferating communicative forms, actions, and situations on the Internet (e-mails, blogs, FAQs, etc.). Focusing on the particular genre of the Internet "posting" in CSCL contexts, the paper hypothesizes that the educational use of this genre bears recognizable similarities with its generic antecedent, the letter. In testing this hypothesis, the paper describes a pilot case study of a set of CSCL postings (n = 136), which attempts to quantify the occurrence of rhetorical characteristics common to both the epistolary and CSCL "genres." This content analysis shows the recurrence in this sample of a range of rhetorical markers (240 in total) that are characteristic of epistolary dynamics. It concludes by considering the implications of these findings and of a "genre approach" for CSCL research generally, and for community of inquiry models in particular.