Gaining insights from a wide range of disciplines, linguistics has become "a prominent academic discipline throughout the world '' (Buttny. R, 1993). This position is mainly achieved through the shift from classical language description and application into tackling 'real world problems'. One important domain of such linguistic application is language pathology, hence, giving rise to the linguistic subfield ` Clinical Linguistics". In Tunisia, the name of the field still not denotes what it really should. Within this frame is held the present paper entitled "On the Contribution of Systemic Functional Linguistic Theory (SFL) to the study of Neurological Condition aphasia''. Its main aim is first to define aphasia and bring into the light the field of clinical linguistics. As theories are developing for the treatment and assessment of speech and language pathologies, a second important objective of the paper is to describe some of the applications of the systemic functional approach to the treatment of aphasic symptoms. Thereafter, the considered approach is compared to the psycholinguistic perspective which, for many decades, has dominated to a certain degree the essence of speech and language pathology. The description of the functional approach along with the comparison to the other perspective highlights to what extent the SFL framework can be privileged to some 'traditional' approaches used in the research on aphasia. However, this claim calls into question the validity of the use of methodological tools originating from traditional approaches in dealing with aphasia in current or future researches.