The aim of this thesis is to look into the main difficulties that individuals affected by autism spectrum disorder (ASD) face in social language use and, more specifically, consider the impairment of presuppositional skills in these individuals. Presuppositional skills in this study refer to the ability to make presuppositions about situations and interlocutors in talk-interactions in order to comprehend the contextual, verbal and non-verbal cues necessary to produce effective communication. In the data analysis, (near-)authentic conversations of two individuals diagnosed within the autism spectrum were carefully transcribed from documentaries and critically analysed to identify impairment of pragmatics and, particularly, of presuppositional skills. This study focused on naturally occurring data, as it is uncommon for studies of language disorders to be based on (near-)authentic interactional data. The results were then compared to previous research in the field to see if the deficits observed conform to the literature. Finally, the strategies used by interlocutors/caretakers to achieve effective communication/tasks were listed in the results section. Some of the main impairments of presuppositional skills identified include difficulty in understanding verbal and non-verbal cues in general, which causes an inability to judge others’ degree of engagement in the conversation, compromises the comprehension of sarcasm, and the understanding of what might be presumed but not stated. Other impairments of presuppositional skills include non-adherence to Grice’s Maxim of Quantity, as in not knowing when to change the conversational topic and the amount of information required to satisfy the listener’s needs, and non-adherence to Grice’s Maxim of Relation, as in producing comments that are not relevant to the conversational topic and introducing new topics that are neither relevant nor of interest to the communicative partner. In addition, an impaired ability to understand reference, difficulty in initiating appropriate conversations, and an inability to adapt language to different contexts were observed. More general pragmatic language deficits identified include the use of immediate or delayed echolalia to express requests and other intentions, difficulties with turn-taking, and the use of repetitive questions and statements to sustain conversations.