The title of this paper — public discourse — is inherently ambivalent, given the multiple use of both terms in scholarly work across disciplines. Of the two, the term ‘public’ is perhaps more problematic because of its everyday use (e.g., public notice, public lecture, public interest, going public). Accordingly, this paper will mainly centre around the notion of ‘publicness’. To begin with, it define ‘public discourse’ as social processes of talk and text in the public domain which have institutionally ratified consequences. For instance, an interrogation of an airline passenger by a customs officer in a secluded space is institutionally grounded and would thus count as public discourse. Viewed from this angle, ‘public discourse’ is different from various versions of the private realm (e.g., family, inter-personal, inner-self etc.). Broadly speaking, the term ‘discourse’ can be taken to mean a stretch of talk or text (including semiotic icons) as well as a form of knowledge and the social processes of production and consumption of such knowledge in the Foucauldian sense. ‘Public discourse’, thus defined, includes what goes under the generic rubric of ‘media discourse’ and ‘political communication’ as well as discourse in organisational and professional settings (for a detailed discussion of the scope of ‘public discourse’ in communicative terms, see Scollon 1997). However, given the limited scope, this paper will link its arguments to media communication where necessary, and only, in passing, touch upon the communicative practices in the organisational and professional domain. The rest of the paper is structured as follows: first, it spells out in detail various readings of the term ‘public’ and the shifting nature of its boundaries. In Section 2, it draws attention to the situation-talk dialectics in communication-oriented public discourse studies, followed by an outline of two dominant frameworks — Goffman and Habermas — concerned with the notions of public behaviour and public sphere in different ways (Sections 3 and 4). In Section 5, It offers a brief overview of the shifting nature of boundary marking between private and public domains with relation to the positioning of the state, pointing out particularly the leakages between these two types of discourse in the contemporary society (as evidenced in the tradition of media and cultural studies). In Section 6, It focuses on the mechanism of information exchange in the public domain, which is particularly relevant to pragmatics research. It briefly refers to the dominant models of ‘pragmatics of information exchange’, which then leads to suggest that a model of social pragmatics (which shares an analytic trend with critical discourse analysis) can be a useful way of understanding the dynamic communicative practices in the public domain.