Results of a study to develop methods, based on UV laser ablation and chemical etching, for repairing defects in phase shifting masks will be discussed. The application of these techniques to a variety of candidate phase shifting mask types including attenuating Cr, embedded shifter Cr and SOG PSM will be discussed. The repair processes will be characterized in terms of process laser wavelength and energy flux, precursor gas type and material removal rate, transmission in the repaired area, and the phase shift, if any, introduced at the repair site. The effectiveness of various optical and gas delivery techniques will be compared with the types of defects likely to be encountered in the candidate masks. The results presented will include repair rate, etching uniformity and transmission data along with SEM and optical micrographs before and after repair events.