The moon offers mixed blessings as a site for astronomical observatories, and some of these are presented in Tables I and II (see the paper by Smith for a more complete discussion). The advantages are so strong that they make the moon a unique site for certain kinds of observatories, particularly those which feature very large telescopes or interferometric arrays of large dimensions, and those that require a presence beyond the screening effect of the earth’s magnetic field. More than one hundred scientists gathered at Annapolis, Maryland for a Workshop on Astrophysics from the Moon (Feb. 5-7, 1990), and discussed these questions in considerable detail (Mumma and Smith 1990). The objective was to examine the astrophysical frontiers of the 21st century, and to identify those which require the presence of astrophysical observatories on the moon for their successful address. The scope of the Workshop was defined to include all areas of space astronomy. It was assumed that the base program of space astronomy will have been completed prior to the emplacement of lunar-based observatories, thus that the four Great Observatories, the Solar and Heliospheric Observatory, the Orbiting Solar Laboratory, the Coronagraphic Imaging and Astrometric Telescope Facility, and the Earth-Orbital Planetary Telescope will all have been accomplished. The Workshop participants tried to look beyond the scientific objectives to be addressed with those Earth-orbiting facilities to the next generation of scientific frontiers, which are associated with the very small, the very distant, and the very faint. This paper summarizes some of the ideas presented there, but these are presented in much greater detail in the published Proceedings (Mumma and Smith 1990).