The effects of bifemelane hydrochloride on aphasia and on cerebral circulation and metabolism were studied using positron emission tomography (PET) in 10 aphasic patients with cerebrovascular disease. After the first PET scan, bifemelane was administered orally three times in a daily dose of 150 mg. Aphasic features, such as fluency, auditory comprehension, object naming, and repetition, were evaluated by using the Western Aphasia Battery (Japanese edition) before and at least 2 months after bifemelane treatment. Simultaneous with the evaluation of aphasia, the PET scans were performed by using the steady-state method with 15O gases inhalation. All aphasic features, except fluency, improved significantly after bifemelane treatment. Regional cerebral blood flow (rCBF) and the cerebral metabolic rate for oxygen (CMRO2) were increased at every brain region of interest, and the oxygen extraction fraction was decreased. Both rCBF and CMRO2 were significantly increased on the left inferior frontal gyrus, superior temporal gyrus, white matter of the parietal lobe, and insula. These results suggest that bifemelane improves both cerebral oxygen metabolism and cerebral circulation and contributes to the improvement of aphasia caused by cerebrovascular disease.