• Six patients manifested progressive language disturbance, resembling aphasia secondary to a focal dominant hemisphere lesion, as either an isolated initial symptom or a prominent early feature of a more generalized dementing illness. None had a history of transient ischemic attacks or stroke, and in all cases an extensive clinical and laboratory investigation failed to show either a focal brain lesion or a definable etiology of dementia. This article discusses the relationship of isolated or early aphasia to known dementing syndromes. Patients who consult physicians for language disturbance should be evaluated and followed up both for evidence of progressive language deterioration and for the development of a generalized dementia.