This article reviews current knowledge about the nature of auditory word recognition deficits in aphasia. It assumes that the language functioning of adults with aphasia was normal prior to sustaining brain injury, and that their word recognition system was intact. As a consequence, the study of aphasia provides insight into how damage to particular areas of the brain affects speech and language processing, and thus provides a crucial step in mapping out the neural systems underlying speech and language processing. To this end, much of the discussion focuses on word recognition deficits in Broca's and Wernicke's aphasics, two clinical syndromes that have provided the basis for much of the study of the neural basis of language. Clinically, Broca's aphasics have a profound expressive impairment in the face of relatively good auditory language comprehension. This article also considers deficits in processing the sound structure of language, graded activation of the lexicon, lexical competition, influence of word recognition on speech processing, and influence of sentential context on word recognition.