Background/Aims: Agitation following traumatic braininjury is characterised by a heightened state of activitywith disorganised information processing that interfereswith learning and achieving functional goals. This studyaimed to identify information processing problems duringtask performance of a severely agitated adult using thePerceive, Recall, Plan and Perform (PRPP) System of TaskAnalysis. Second, this study aimed to examine the sensitivityof the PRPP System to changes in task performanceover a short period of rehabilitation, and third, to evaluate theguidance provided by the PRPP in directing intervention.Methods: A case study research design was employed. ThePRPP System of Task Analysis was used to assess changesin task embedded information processing capacity duringoccupational therapy intervention with a severely agitatedadult in a rehabilitation context. Performance is assessedon three selected tasks over a one-month period.Results: Information processing difficulties during taskperformance can be clearly identified when observing aseverely agitated adult following a traumatic brain injury.Processing skills involving attention, sensory processingand planning were most affected at this stage of rehabilitation.These processing difficulties are linked to establisheddescriptions of agitated behaviour. Fluctuations in performanceacross three tasks of differing processing complexitywere evident, leading to hypothesised relationships betweentask complexity, environment and novelty with informationprocessing errors. Changes in specific information processingcapacity over time were evident based on repeated measuresusing the PRPP System of Task Analysis. This lends preliminarysupport for its utility as an outcome measure, and raiseshypotheses about the type of therapy required to enhanceinformation processing in people with severe agitation.Conclusions: The PRPP System is sensitive to informationprocessing changes in severely agitated adults whenused to reassess performance over short intervals and canprovide direct guidance to occupational therapy interventionto improve task embedded information processing bycategorising errors under four stages of an informationprocessing model: Perceive, Recall, Plan and Perform.