Publisher Summary This chapter discusses the influence of localized surface states on the optical properties of alkaline metals. The dielectric properties near a surface change continuously from ɛ = 1 to the bulk dielectric function (DF), ɛb (ω). In the approximation calculated in a layer, defined by the penetration depth al of the light, effective DF, which includes the surface effects, is presented in the chapter. With this ɛ, the classical formulas for the reflectivity can be used. In a simple model for the surface potential, consisting of the bulk pseudopotential inside the metal and two steps (simulating adsorbates) at the surface, bulk dielectric potential is calculated. The results obtained are—it is highly anisotropic, it can be of the same order as the bulk contribution but its magnitude depends strongly on the potential parameters near the surface, and it is zero in the case of a clean surface.