Abstract: This thesis investigates the linguistic and cultural resources that eight Indigenous children draw on when they pursue affiliative and disaffiliative actions in talk with peers. These children are L1 speakers of Murrinhpatha, a traditional Australian language spoken in and around the remote Aboriginal community of Wadeye, in the north of Australia. Just as the linguistic context these children are growing up in is unique, so is their sociocultural context. While increasingly informed by Western culture, Murrinhpatha speaking society at Wadeye is still to a large degree organised around traditional Aboriginal identity categories, involving connections to ‘country’ and ‘totem’, as well as more universal categories such as gender. Communicative exchanges between children are thought to be highly revealing of their linguistic and socio-pragmatic abilities. Peer talk is also viewed as a site in which children’s understandings of the world play out. This is particularly true when category terms are employed in spoken interactions. Categories are held to index local common-sense knowledge about ‘types’ of people or personae and how they behave. In any given interaction, the category term an individual selects, and the action they pursue with it, offers a window onto that speaker’s sociocultural world, as does the way in which their interlocutor responds to its use. By investigating children’s productions of category terms in interactions with peers, not only are children’s linguistic capabilities illuminated but also aspects of their cultural understandings. The data drawn on in this study is spontaneously occurring speech, which was recorded at four regularly spaced intervals over 21 months, resulting in a corpus of child speech spanning the ages of 2;10 to 7;2 years. The data was analysed using Membership Categorisation Analysis (MCA), and was done so to produce a broad description of how the cohort uses categories when pursuing affiliative and disaffiliative actions with peers at different ages. This study is one of the very few on Indigenous children’s interactions, and the first to apply MCA. It also appears to be the first MCA study to investigate the use of social categories which do not exist in the Western world. The application of MCA in this thesis is also novel in terms of the scope of its analysis and its descriptive aims. A secondary goal for this study was to maximise comparability with existing studies on children’s talk, a task that, owing to the specific nature of interactional analyses, is often a challenge. While this study does not focus on children’s individual development, findings appear to indicate certain age-related uses of categories in talk. The use of categories by the cohort suggest that from 3 to 6 years of age children move from a focus on themselves as individuals, to experimenting with categories and the interactional clout they can afford, to operating as a member of the broader social group, using categories predominantly to maintain the local moral order. Comparisons with descriptions of children from other linguistic and cultural backgrounds reveal numerous similarities and differences in terms of the selection and application of categories. For example, Aboriginal categories of land appear to be used by some of the Murrinhpatha speaking children in a similar way to notions of friendship by children in Western societies. Through the analysis of children’s use of categories, this study reveals these Murrinhpatha speaking children to be at once ‘just’ children as well as children from a highly specific cultural and linguistic context, and impresses the need to examine language in relation to a speaker’s sociocultural environment.