A Welsbach metal-quartz ozone generator operated as a discharge reactor and simultaneously UVC-irradiated was used to convert anal.-grade O-2 (H2O < 1.4 ppm), 4 L(S.T.P.)/h, into O-3. Ozone yield was related to temperature and presence of catalyst at the discharge gap and also to UV ray wavelength. At 0degreesC of the metal electrode + UV rays, the catalyst gave a distinct though minor increase in O-3 concentration; at discharge powers of 15-20 W, O-3 concentrations were ca. 7 mol%. The effect had a limited range. In the unpacked ozone generator, UV rays of longer wavelengths gave inferior results.