Two brothers presented with slowly progressive aphasia. One brother, who became behaviourally disturbed only at the end of his illness, was found at necropsy to have predominant left frontotemporal atrophy. The other brother developed severe behavioural disturbances shortly after the onset of language impairment. His brain revealed bilateral frontotemporal atrophy. In both there was non-Alzheimer's disease pathology with the histological features of loss of large cortical nerve cells, spongiform change and mild gliosis. The differential anatomical atrophy supports the view that clinical manifestations of lobar atrophy are dictated by the topographical distribution of a common underlying pathology, linking the syndromes of progressive aphasia to dementia of frontal lobe type (DFT) and DFT with motor neuron disease.