Prospective and retrospective language evaluations and single photon emission computed tomography (SPECT) scans were performed in order to study the relationship between post-stroke recovery from aphasia and changes in cerebral blood flow (CBF) in groups of patients who had made a good recovery and those who had not. For the prospective study, 20 right-handed patients with aphasia secondary to an acute cerebrovascular accident (CVA) in the left middle cerebral artery territory received language evaluations with a Japanese Standard Language Test of Aphasia (SLTA), and SPECT scans performed twice, at a mean of 3.2 and a mean of 9.2 months post-onset. Only one slice of SPECT data was analysed. A significant correlation was observed between the severity of the initial language deficit and initial CBF on the left side, but not the right. Initial CBF was not a predictor for future language recovery in either hemisphere. There was a correlation between the change in the left mean hemispheric CBF (but not the right) and the change in the overall SLTA severity rating from 3 to 9 months post-stroke. In the retrospective study, 16 right-handed patients with residual aphasia secondary to CVA in the left middle cerebral artery territory received SLTA and SPECT at a mean of 82.8 months post-onset. The patients had also received initial language evaluation with SLTA at a mean of 6.5 months post-onset. In contrast to the prospective study, the results demonstrated that the mean left hemispheric CBF at approximately 7 years post-onset did not differ between good and poor recovery groups. However, the mean right hemispheric CBF of the good recovery group was higher than that of the poor recovery group in the frontal and the thalamic regions, and also in the left frontal region. The results of these complementary studies suggest that the initial language recovery within the first year post-onset may be linked primarily to functional recovery in the dominant hemisphere, where an increase in CBF was observed at 9 months post-onset. The increased perfusion adjacent to the lesion may be crucial for early recovery in aphasia. Subsequent language recovery and the long-term recovery in aphasia may be related to slow and gradual compensatory functions in the contralateral hemisphere, specifically in the homotopic frontal and thalamic areas.