The application of diamond electrodes is promising for electrolyzing water to produce ozone because of their superior chemical and dimensional stability, as well as their large overpotential for the oxygen evolution reaction. A freestanding conductive diamond plate was perforated to prepare a freestanding perforated diamond electrode, which was incorporated into a zero-gap electrolytic cell for direct electrochemical ozone-water production. This system has many advantages, in particular, that it exhibits the highest current efficiency (29%) reported for the electrochemical ozone-water production thus far. (c) 2006 The Electrochemical Society.