This thesis investigates a range of everyday interactions of traumatic brain injury (TBI) subjects when compared with control subjects to examine whether there are differences in the overall structure of interactions, in the way information is exchanged and in the wording which is used. Analyses from systemic functional linguistics including generic structure potential analysis, exchange structure analysis and analysis of politeness markers were used to examine the interactional impairments reported to follow TBI. Results indicated that TBI subjects differed from controls in their use of interpersonal language resources. These differences were exaggerated when subjects were interacting with someone in authority. When placed in a more powerful role, TBI subjects were able to utilise language resources to a similar extent to controls across the three levels of analysis. This thesis has important implications for the assessment and management of interactional communication impairments which may follow TBI, including suggestions for therapy with the person with TBI and for communication partners of people with TBI including therapists, family members and the community.