We describe an analysis of lexical processing performed in a patient with the acute onset of an isolated anomia. Based on a model of lexical processing, we evaluated hypotheses as to the source of the naming deficit. We observed impairments in oral and written picture naming and oral naming to definition with relatively intact semantic processing across input modalities, suggesting that output from the semantic system was impaired. In contrast to previous reports, we propose that this pattern represents an impairment that arises late in semantic processing prior to accessing mode- specific verbal and graphemic output Lexicons. These deficits were associated with a lesion in the posterior portion of the middle temporal gyms or area 37, an area of supramodal association cortex that is uniquely suited as a substrate for the multimodal deficit in naming.