Abstract: An apparatus and method for ozone generation and a method for generating ozone by exposing oxygen to high frequency alternating current with high voltage over a dielectric. The apparatus comprises a pressure compensation admitting unit joined together by at least two plates of a dielectric material and therebetween a present electrode on which high frequency alternating current with high voltage is applicable, and two sealed spaces for generation of ozone on opposite sides of the unit, whereby the respective sealed space, on the opposite side of said plate of dielectric material, is delimited by an earthed and cooled electrode, through which oxygen gas or gas rich in oxygen is supplied to the space and ozone is conducted out of the same. By means of this apparatus, oxygen gas or gas rich in oxygen can be conducted under pressure into sealed chambers on opposite sides of the pressure compensation admitting unit.