This presentation will review the key aspects of advanced photomask manufacturing and highlight the major technical challenges facing the mask industry. The bulk of the discussion will focus on mask technology for optical (248nm - 193nm wavelength) lithography, seen industry wide as the front up approach for 250nm to 180nm wafer dimension processing. After briefly establishing the business environment in which advanced optical mask development is done, current and future mask specifications are presented, the basic chrome on glass mask process is reviewed, and the major technical challenges facing each process segment are discussed in the context of high resolution lithography requirements. The basic principles involved in the two most mask intensive resolution enhancement techniques, optical proximity correction and phase shifted masks (alternating as well as attenuated) are reviewed and their specific technology challenges presented. A brief discussion of mask challenges in proximity x-ray lithography, the only viable near in alternative to optical lithography for this resolution range, will close out this presentation. The material is targeted at the general VLSI manufacturing and development community, it is not intended as a training course for mask development engineers.