- To investigate the pattern of hemispheric activation, according to cerebral blood flow changes, as measured by Transcranial Doppler Ultrasonography (TCD) during language tasks in stroke patients with aphasia. Prospective study investigating results of TCD monitoring during language naming and recognition tasks in ischemic stroke patients (n = 32) with and without aphasia and 5 control subjects. Delta mean flow velocity (MFV) in the left Middle Cerebral Artery (MCA) was found to be much lower in aphasia patients as compared to healthy subjects. Negative statistical correlation was found between the improvement of language ability and the blood flow velocity parameters in the left hemisphere. Aphasia patients with good language ability showed much higher MFV in the right MCA during the first test. Left hemispheric blood flow velocity shift was found to be higher during speech tasks in the patients with poor language ability. Our study suggests that the performance of language tasks in aphasia patients during early recovery after stroke is associated with relatively high right hemisphere activation. High blood flow velocity in the right MCA of aphasia patients was found to be a good prognostic sign for better language ability. Arterial blood flow that shifted towards the left hemisphere during speech tasks was associated with poor language ability.