This article analyses an experience in collaborative learning in an asynchronous writing environment through discussion forums on a WebCt platform of the University of Huelva's virtual campus, and was part of an innovative teaching project in 2007-08. The main objectives are to describe the processes of collaborative knowledge construction and the relevance of many-to-many communication in collective case resolution in asynchronous writing contexts. Two cases were selected for the experience, and two analytical approaches were adopted: discourse analysis and social network analysis. The results show that in the Case A group, where speech occurrence was less prevalent, the social network analysis markers show considerable cohesion and low levels of network centrality. By contrast, speech prevalence was greater in the Case B group and the network centrality markers were higher, although the group was less cohesive. These results lead to the hypothesis that many-to-many communication is more important in collective knowledge generation processes than dyadic or triadic communication. (Contains 6 figures and 4 tables.)