Lead-plating for superconducting rf resonators historically has been directed toward reducing grain size and eliminating spikes on the surface. At present smooth, spike-free, bright lead surface are obtainable, but there is little correlation between appearance and performance. Even the best lead-plated resonators fall short of the BCS limit and exhibit impenetrable low level multipacting barriers. Investigations were made of degassing lead-plated surfaces under rf resonant electron discharge or multipacting. The mass-spectra of the residual atmosphere showed that decomposition of hydrocarbons on the surface took place. Discolouration of the lead surface, due to the formation of a carbon layer, was easily observed. A method of cleaning surfaces by ion bombardment employing chemically active gases, was proposed and tested. An rf discharge, initiated by multipacting at a pressure of 10 −2−10 −1 Torr was used. The first step, discharge treatment in a CO 2 atmosphere, assures oxidation of carbon and hydrocarbons into gaseous compounds which are removed by pumping. During the second step, discharge treatment in a hydrogen atmosphere, lead oxides are reduced to metal.