This article presents a five-tiered taxonomy that describes the nature of participation in, and learning through, asynchronous discussion. The taxonomy is framed by a constructivist view of asynchronous discussion. The five tiers of the taxonomy include the following: (a) passive participation, (b) developmental participation, (c) generative participation, (d) dialogical participation, and (e) metacognitive participation. This article concludes with implications for pedagogy and suggestions for the direction of future theoretical and empirical research.