This thesis is a consideration of the insights into acquired language disorder which can be obtained via recent developments in generative grammar, a syntactic framework which investigates how language might be acquired, how it is represented in the mind/brain, and (indirectly) how it might break down following trauma to the brain. The case of MC, an aphasic patient, is presented in detail, and an account of his language difficulties is proposed. MC is very impaired at the production of functional categories and morphologically complex substantives in isolation, whereas he has relatively good understanding of such items, and is able to use them more appropriately in connected speech or reading of texts rather than single words. It is hypothesised that he demonstrates the effects of a deficit at the level of an isolable component of the language faculty which deals solely with morphological processing. A deficit at this level results in failure to assign realisations to functional categories (unless they are in a sentential context, in which case their representation is supported by the syntactic component), accompanied by errors of derivational and inflectional affixation, but relatively intact comprehension of the same items. Data obtained from MC are presented in extenso, and shown to support this explanation for his language performance. This case study also provides the opportunity to evaluate empirically various aspects of linguistic theory, and three such domains are presented here. The case of MC provides support for an analysis of unaccusative verbs as functional heads; for prepositions as forming part of the functional lexicon; and for adverbial expressions being analysed as associated with the projections of functional categories. Insights into the underlying nature of MC's language difficulties would not have been possible if the case had not been placed into a coherent theoretical context. and the account of a morphological deficit provided here is shown to have some empirical utility with reference to an existing case from the neuropsychological literature. The mutual benefit of neuropsychological and linguistic investigations of this kind is emphasised.