Distinguishing dementia lacking distinctive histologic features and primary progressive aphasia requires a clinicopathological point of view. These syndromes do not overlap on clinical grounds, but can have similar histological features. Dementia lacking distinctive histology has a clinico-pathologic definition. Cases with frontal lobe type symptoms and signs, and fronto-temporal lesions lacking any neuropathological markers are classified as ''frontal lobe degeneration of non-Alzheimer type'', ''dementia of frontal type'', or ''dementia lacking distinctive histology''. Fronto-temporal atrophy, sometimes asymmetrical, may be present. Cortical degeneration lacking distinctive histology (neuronal loss, gliosis and spongiosis of layers II-III of the affected cortex) is the only constant histopathological finding. Primary progressive aphasia has a clinical definition: ''a gradual dissolution of language is the only salient feature for at least two years'' (Mesulam and Weintraub, 1992). This condition is usually associated with focal cortical atrophy. Depending on the bulk of pathology, anomic aphasia or pure verbal deafness, and less frequently pure anarthria, can be observed. Pick disease, Alzheimer disease or cortical degeneration lacking distinctive histology can be involved. That cortical degeneration lacking distinctive histology is a unique entity cannot be asserted before its precise genetic and biochemical nature could be demonstrated.