The effect of acetyl-L-carnitine on cerebral blood flow was evaluated in ten patients with cerebrovascular disease, who suffered an ischaemic stroke at least six months before the study. All patients performed a computerized tomograph scan and were investigated by Xenon 133 using a brain dedicated Single Photon Emission Computerized Tomography. Acetyl-L-carnitine was administered intravenously (i.v.) at a dosage of 1.5 g. Cerebral blood flow (ml/min. 100 g) was evaluated before and 45 min after the injection. Cerebral blood flow improved in both the ispilateral and controlateral hemisphere of the ischaemic area, but not in the stroke corresponding zone. It is concluded that acetyl-L-carnitine at a dosage of 1.5 g i.v. improves cerebral blood flow in patients with cerebrovascular disease.