Cerebral blood flow in progressive aphasia without dementia. Case report, using 133xenon inhalation, technetium 99m hexamethylpropyleneamine oxime and single photon emission computerized tomography. We report a case of progressive aphasia without clinical signs of intellectual or behavioral impairment, satisfying Mesulam's clinical criteria of primary progressive aphasia, as 4 yrs of extensive psychometric testing and radiological imaging, comprising CT and MRI, failed to detect evidence of relevant involvement outside the left perisylvian regions. Cranial CT was normal but MRI showed multiple bilateral lesions in the deep white matter. Cerebral blood flow (CBF) studies by single photon emission computerized tomography, however, showed an initial frontotemporal focus of hypoperfusion that progressively extended to include most of the ipsilateral hemisphere and the contralateral frontal lobe. This suggests that CBF imaging may yet be the most sensitive technique in revealing subclinical injury in the degenerative brain diseases of focal onset. 