Speech and language functions were assessed in 18 patients with multi-infarct dementia (MID) and 14 with dementia of the Alzheimer type (DAT). The age range and dementia severity of the two groups were comparable. We used a speech and language battery assessing 37 elements of verbal output to characterize alterations in the patients. MID patients had more abnormalities of motor aspects of speech, whereas DAT patients had empty speech, more marked anomia, and relative sparing of motor speech functions. The results demonstrate that speech and language differ in MID and DAT. In addition, MID patients exhibited common clinical features despite the heterogeneity of the syndrome.