Numerical computations are performed to show that locally sunlit areas in the dark lunar sunset terminator region can acquire large electric potentials and fields due to retention of photoelectrons emitted from sunlit areas by surrounding dark areas of the highly resistive lunar surface. For the simple model considered it is shown that for the emission of monoenergetic electrons of energy ϕ eV the potential of the sunlit area can exceed 2ϕ V. For the centimeter-scale sunlit area considered, electric fields in excess of 2ϕ V/cm are generated over a large portion of the sunlit area. The fields are particularly intense at the sunlight-shadow boundary. Various aspects of the problem are examined, and it is concluded that the mechanism suggested can indeed occur in the lunar sunset terminator region. The discussion in this paper has particular relevance to the understanding of the lunar 'horizon glow' phenomenon and to the problem of electrostatic transportation of lunar dust.