Experiences identified by channel expansion theory as contributing to media-use knowledge bases were hypothesized to be positively related to the perceived richness of a communications channel. We investigated the hypotheses, using electronic mail as the channel, in both a cross-sectional and a multiwave study. Results varied for types of experience and generally supported channel expansion theory. Channel use, perceived social influence, and the dynamic nature of richness perceptions were also investigated. Implications of these findings are discussed.