This article reports a grounded theory study of the moderation of asynchronous online discussions, to explore the processes by which tutors in higher education decide when and how to moderate. It aims to construct a theory of e-moderation based on some key factors which appear to influence e-moderation. It discusses previous research on the definition and practice of e-moderation, and then describes the study, which involved four e-moderators working in two different university contexts. Key themes on e-moderation, which emerged using a grounded theory approach, are discussed. It proposes a framework for e-moderation and suggests that as a facilitative activity, it should be sufficiently contained within a ring-fenced learning arena. Factors outside and inside the ring-fence that appear to influence e-moderation and their implications for future theory development and validation are discussed. (Contains 1 table and 1 figure.)