Electron projection lithography (EPL) requires mask formats that are significantly different from those used in traditional optical lithography. These masks must consist of a thin membrane that is either patterned with transmissive perforations for stencil masks or patterned with a scatterer layer to form a continuous membrane mask. In this paper, the critical requirements for fabrication of EPL masks are discussed. Challenges for mask blank fabrication, image size uniformity, image placement accuracy, and defect control are presented with examples from mask fabrication. The impact of these parameters on EPL mask cost is then discussed. The mask cost is compared for different critical device levels and for different chip sizes. The influence of mask parameters and need for complementary masks drives higher mask costs for certain device levels. By examining the factors influencing mask cost for certain levels, the areas of mask technology that are most critical to controlling mask cost can be identified.