Most research on dialogue has concentrated on dialogues involving two interlocutors. In this paper we consider the nature of multi-party dialogues. We discuss whether some of the important characteristics that have been identified in two-party dialogues and the theoretical accounts that have been proposed for them are also applicable to multi-party dialogues. We argue that the way in which common ground is accumulated in multi-party dialogues differs from the way in which it is accumulated in the two-party dialogues that have commonly been studied. However, we argue that these differences are related to particular characteristics which tend to be associated with either two-party or multi-party dialogues but are not inherent to them. We show that these characteristics can account for differences between different types of two-party and multi-party dialogues, including effects of group size, and we propose that the same fundamental principles underlie behaviour in both two-party and multi-party dialogues.