Background: Perseveration is a frequently encountered characteristic of individuals with organic brain involvement, including individuals with traumatic brain injury (TBI). Current theory implicates disordered executive functioning, particularly deficient inhibitory control, in the manifestation of perseverative phenomena (McNamara & Albert, 2004). To date, no work has been published related to conversational data despite numerous allusions in the literature to the presence of perseveration during conversational discourse. Existing research indicates that pharmacological approaches to reduction of verbal perseveration may be effective, although no full-scale clinical trial of any pharmacological agent targeted specifically at reducing perseveration has been conducted (McNamara & Albert, 2004). Aims: This study examines conversational correlates of perseveration in TBI, the accompanying executive functioning profiles in relation to Barkley's hybrid model of executive functioning and self-regulation (1997) and responses to pharmacotherapy (Ritalin). Methods & Procedures: Two participants, in chronic stages following TBI with prefrontal and sub-cortical damage, participated in parallel case studies with a quasi-experimental research design. Baseline, active, placebo, and withdrawal phases were included as well as double blind and randomisation precautions. Conversational data were generated using Conversation Analysis. Neuropsychological data were generated following a full battery of tests investigating behavioural inhibition, nonverbal working memory, internalisation of language, regulation of affect, and reconstitution. Outcomes & Results: Conversational data demonstrated disturbed topic management as a result of verbal perseveration. Participant AA demonstrated recurrent perseveration while PB demonstrated stuck-in-set perseveration, which influenced their conversations in highly specific ways. These findings were accompanied by discrete profiles indicating unique disruptions of executive functioning, particularly in relation to behavioural inhibition. Deficits in attention impacted profoundly on self-regulating functions, in particular nonverbal working memory and reconstitution. Improvements were noted during active drug phases related to improved behavioural inhibition and subsequent amelioration of perseverative manifestations with some evidence of improved topic shift and contribution and greater capacity for reconstitution and working memory tasks. Context was found to exert significant effects in relation to perseveration and its conversational manifestations. Conclusions: Perseveration co-exists with marked deficits in behavioural inhibition, which differentially affects executive functioning abilities, resulting in discrete cognitive profiles with corresponding conversational outcomes. Positive responses to pharmacotherapy present optimistic potential for future treatment, while context variables highlight the need for individualised, data-driven intervention programmes with an emphasis on continuous conversational interaction to preserve and improve communicative skills in individuals with chronic TBI.