Transcranial Doppler sonography (TCD) was performed in a case of migraine with aura during the different phases of the attack. In the prodromic period our patient showed a slight central deficit of the seventh right cranial nerve and hypesthesia in her right arm. TCD indicated a remarkable decrease of the mean flow velocity (MFV) of the left middle cerebral artery (MCA). During the headache phase and when the signs and symptoms subsided, TCD showed an increase in MFV of both middle cerebral arteries with normal symmetry. An electroencephalogram (EEG) demonstrated a left temporal disorder. A month later a cranial CT scan, an EEG, and TCD were normal. In our opinion all these findings suggest a focal reduction in cerebral blood flow in the prodromic phase.