Ubiquinone(-10), known as a component of the electron transfer system in many organisms, has been used for the treatment of heart disease. No attempt at developing an approach for overproduction of ubiquinone by genetic engineering has been reported, presumably because of the limited number of genes involved in ubiquinone biosynthesis have been cloned. In the present study we overproduced ubiquinone in Escherichia coli using all available genes involved in ubiquinone biosynthesis. Two genes were found to be important for the production of ubiquinone, ubiA, which encodes p-hydroxybenzoate-polyprenyl pyrophosphate transferase and ispB, which encodes polyprenyl pyrophosphate synthetase. We succeeded in achieving a level of ubiquinone production three times that of the wild-type cells by genetic engineering.