A classical task in the neuropsychology of language is sentence-picture matching. In this task subjects are required to select a picture from a set of alternatives that matches an auditorily presented sentence. We developed an on-line version of this task, by showing a picture and presenting a sentence while recording the patients' ERP. Sentences differed in complexity, and ranged from simple active semantically irreversible sentences ("The young lady reads the exciting book") to passive, semanticaaly reversible sentences ("The woman is pushed by the tall man"). The sentence either matched the picture or mismatched the visual information depicted. Both elderly control subjects and patients with Broca's aphasia were tested with this paradigm. Elderly controls showed on-line sensitivity to the mismatch as soon as the verb was heard, and thereby the thematic role information was made available. The aphasic patients did not show an on-line ERP effect. However, they showed an off-line behavioral sensitivity to the mismatch between sentence and picture. The patients' dissociation between on-line and off-line sensitivity will be discussed in relation to the nature of the underlying language deficit in the aphasic patients.