Recent approaches to the study of language disorders in adults with focal brain damage (aphasia) have interpreted aphasic symptoms as impairments of particular aspects of the normal language system. Two distinct approaches along these lines, clinical linguistics and cognitive neuropsychology, have developed in parallel. Although there are differences between these approaches, there is also considerable methodological and substantive overlap. These similarities and differences are reviewed, with particular emphasis on the contributions of each approach to the development, implementation and interpretation of treatments for aphasic disorders of sentence production. It is argued that the field of clinical linguistics has defined and addressed numerous problems that cognitive neuropsychologists are beginning to confront as they attempt to use models of normal language processing to motivate treatment for aphasia.