This study is concerned with the structural analysis of a corpus of discussive data. The data, mainly taken from CANCODE, the Cambridge and Nottingham Corpus of Discourse in English, was taken from a range of situational contexts, along a cline of formality from informal ‘chat’ to public broadcast material. The data was analysed using a version of the Sinclair and Coulthard (1975) model of discourse, which was adapted to deal with spoken discussion, and the resultant analytical framework was described in detail. Previous studies of discussion and argumentation have looked either at intra-turn structure, or at the local management of disagreement between turns. This study aims to provide an overall analysis of the structure of discussion, with a view to elucidating the argumentative and persuasive strategies used by interactants involved in spontaneous spoken discussion. It is argued that discourse acts can be identified through the study of certain lexico-grammatical items which typically realise them, and that both at act level and at move level elements of structure combine to form a type of patterning which is typical to discussive texts. It is further argued that this patterning reflects various aspects of the ‘nature’ of discussion, such as its combativeness, and the way that interpersonal objectives become less important in this type of interaction. Also the emergent nature of opinion in discussion is reflected in interactants’ use of focussing moves and summarising acts, and points of convergence between interactants can be identified through their use of responding moves.