Abstract
The dielectric screening of a disordered conductor is reviewed. The effects of interactions on the density of states (DOS) and the related dimensional cross-over in the weakly localized regime are discussed. After discussing the role of the relevant time-scale for determining which of the DOSs appears in the conductivity and dielectric constant, a self-consistent picture is presented for the combined effect of the localization and interaction near the transition in the metallic phase. The results are compared with experiments.