My title is so inclusive that it is not possible to find significant subject matter not in direct conflict with the specialists’ talks scheduled throughout this Colloquium. I intend, however, to emphasize areas where it is probable that much remains to be done. From the Kiel group come printouts for a large family of models, first for hydrogen and recently for helium-dominated atmospheres, which D. Koester has kindly made available. Hydrogen atmospheres for a wide variety of temperatures by Shipman and McGraw and Shipman exist also in computer printout form. Models of mixed He/H composition are less available, but are being prepared. Some hydrogen-deficient stars are the richest in metals, so that models for a variety of metal/helium ratios will need to be computed, and synthetic spectra. Clearly, further models with differing C/He ratios are needed. The successful observations in the ultraviolet with the IUE also demand computations of Lyman-α profiles using modern broadening theory, and a few now exist (Koester 1979). Present observational capabilities require quite detailed predicted fluxes and He II, He I line profiles.