Research on spoken language has mainly focused on spoken discourses in settings such as classroom and workplace. Another important use of speech, casual conversation, has received much less attention. Casual conversation is a functional and semantic activity. It is a site for the establishment and development of social identity and interpersonal relationships; a way of conveying who we are and of interacting with others in different contexts. This paper reports a comparative study on two casual conversations, which naturally occurred in two different settings; between international students from different language backgrounds and between native speakers of English. The texts were constructed in everyday social settings and reflected the role of language in the construction of social identities and interpersonal relations. The two settings displayed different uses of language to construct solidarity, intimacy and affiliation. The study used a functional and semiotic theoretical framework for analysing casual conversation, in order to describe and explain two aspects of casual talk; namely involvement and humour. Using a bottom-up approach, the conversations were analysed to look at the use of naming, technicality, swearing and slang for the purpose of involvement. Humour in each conversation was analysed through language devices that triggered laughter from participants. Situational and cultural influences on meaning-making were explored and compared in the analysis of involvement and humour in the two different settings.