Improvement of energy metabolism in ischemic cerebral tissue benefits the therapy of occlusive cerebrovascular disorders. In the present study, the effects of 6-(10-hydroxydecyl)-2,3-dimethoxy-5-methyl-1,4-benzoquinone (idebenone) on neurological signs, such as ischemic seizures, lactate and ATP contents of the cerebral cortex, and local cerebral blood flow, were assessed in stroke-prone spontaneously hypertensive rats (SHRSP) with experimentally induced cerebral ischemia. Experimental cerebral ischemia was caused by bilateral carotid artery occlusion (BCAO) in male SHRSP (8-10 weeks old). Pretreatment with idebenone (10-100 mg/kg, p.o.) for 3 or 10 days delayed the onset of ischemic seizure (acute stroke) and prolonged survival time in SHRSP roughly in a dose-dependent manner. When the compound (100 mg/kg, i.p.) was given once 30 min after BCAO, it exerted similar ameliorating effects on the neurological deficits. When idebenone (100 mg/kg for 3 days) was given orally, it did not significantly inhibit the decrease in regional cerebral blood flow induced by BCAO. However, the same treatment markedly inhibited increases in the lactate content and lactate/pyruvate ratio and the decrease in ATP content of the cerebral cortex. The compound did not affect cerebral blood flow in normal rats. These results suggest that idebenone ameliorates the neurological deficits related to cerebral ischemia, and that this effect is mediated by improving cerebral energy metabolism.