Recent topics on the biochemical and clinical aspects of ubiquinone are reviewed in this paper. Dallner and his colleagues have demonstrated that ubiquinone is synthesized, not only in mitochondria, but also on the endoplasmic reticulum-Golgi system of the rat liver. New clinical studies that reduction of ubiquinone levels and cardiac functions was induced by treatment with lovastatin, a HMG-CoA reductase inhibitor, have been reported by Folkers et al. According to recent findings, a greater part of ubiquinone in rat and human tissues exists as a reduced hydroquinone form of ubiquinol. On the other hand, good evidence for the antioxidative activity of ubiquinol was obtained from experiments using phosphatidylcholine liposomes and low density lipoprotein.