Abstract This paper sets out to identify, in information-processing terms, the elementary functional components of the mental lexicon and their interrelations. In particular it is concerned with the independent status of lexical codes for written and spoken language, and their relations to each other and to a language-free cognitive representation. Our evidence is based on the performance of language transcoding tasks (such as reading aloud or writing to dictation) in brain-damaged adult subjects. We review evidence for the functional independence of non-linguistic, cognitive representations, and for word-specific, lexical codes in both phonological and orthographic form. The data rule out the hypothesis of a modality-free or abstract lexicon mediating communication between lexical and cognitive representations. The data also reject the dominance of phonological over orthographic codes in access to and from word meanings. We can find no satisfactory evidence for independent lexicons used in language reception and language production.