The extensive work done on the structure of monolingual discourse is now paralleled by a strong tradition of studies of the conversational functions of bilingual codeswitching (Gumperz, 1982; Myers-Scotton, 1993a; Auer, 1998a). So far, however, no direct comparisons have been made between the two. In this paper we compare the way in which four common conversational functions are realised (a) monolingually and (b) through codeswitching by members of a Punjabi and English-speaking network in London. The samples are thus ideally matched - the same speakers in the same context - and we establish that codeswitching may be used in two ways within these conversations. On the one hand it may take the place of monolingual ways of marking significant moves in the conversation (e.g. emphasis, change in voice quality), or add itself to these to reinforce the effect. On the other hand it can be used as a further dimension to the monolingual means which are available, allowing the speakers to introduce structural contrasts, manage the conversational ‘floor’, or highlight the different connotations of each variety as a counterpoint to the referential meaning of their utterance.