The name idebenone (CV-2619) was given to a synthetic compound the chemical structure of which is 6-(10-hydroxydecyl)-2,3-dimethoxy-5-methyl-1,4-benzoquinone (commercial name in Japan: Avan). Although it is insoluble in water, suspensions of it can be applied and are absorbed relatively well from the intestine. Its acute toxicity is very low, and is well tolerated also in subacute and chronic treatments. It displayed no immunogenic or mutagenic side effects in the models studied so far. Pharmacological studies of idebenone revealed that (i) it acts as a free radical scavenger and protects the mitochondrial membrane against lipid peroxidation; (ii) it prevents platelet aggregation; (iii) it improves vascular disorders due to strokes or experimental cerebral ischemia; (iv) it recovers the cholinergic and monoaminergic changes in the ischemic brain; (v) it improves overall brain function (including memory, also) in various animal models. Pharmacokinetic studies have confirmed that it reaches the brain cells even after per os administration. The main conclusion from the experimental data was that idebenone may be of beneficial effect for the neurological disorders related to cerebral ischemia even in humans: the results obtained so far in human clinical trials confirmed the validity of this expectation for cases of human cerebrovascular disease.