The paper outlines the principal characteristics of the effects of irradiation on the discharge current in an ozonizer. The "electronic surface charge theory" of the effect developed by Deb and Ghosh, on a suggestion of Mitra, is explained and is further extended by taking into account the role played by the negative ions formed in the discharge space. It is assumed that the effect of irradiation is to decrease the charges deposited on the surface and to increase those in the volume. The former reduces the discharge current due to the neutralization of the surface charges and the latter increases the main discharge current due to the applied voltage. The net effect is generally a decrease if conditions are favorable for the capture of the electrons in the volume by neutral gas molecules, leading to the formation of negative ions. In all other conditions the effect is generally an increase. It is shown that the theory, in its extended form, is able to account for the origin and the characteristics of both the positive and the negative effects. Numerical calculations of the various rate processes involved in the proposed mechanism are also made. It is shown that the relative magnitudes of these processes are such as to support strongly the "electronic surface charge theory" of the effect.