Functional therapy tasks are frequently cited as being important for the successful carry-over of treatment objectives. Service encounters, such as shopping or enquiring for information on the telephone, are typical community integration activities used with the traumatically brain injured (TBI) population. This paper explores the use of systemic functional linguistics in the measurement of performance in service encounters using Generic Structure Potential (GSP) analysis. Results are presented for GSP analysis of service encounters on the telephone to a bus timetable information service, and the police, for five TBI individuals and five matched controls. Service encounters differed according to the complexity of information requested and the interpersonal, or tenor relationships between participants. Differences were evident between TBI and control interactions in the use of generic structural elements. Variation in generic structure was demonstrated across the two types of service encounter. The potential of GSP to measure the dynamic linguistic patterns in everyday TBT interactions is discussed
