A model of the lexicon and how it is accessed in speech production and perception is proposed using data from both normal and aphasic subjects. Evidence will be presented from a case study of an acquired “surface dyslexic” to show that there is no direct semantic interpretation of the acoustic signal but that it must first be transformed into an abstract phonological representation before meaning is assigned. The interconnecting pathways between phonological, orthographic, and semantic representations in the lexicon of a normal speaker and a language disordered speaker are discussed, as are the various types of processing rules in reading, writing, speaking, and understanding.