Localization effects on the superconducting transition temperature T c are examined in strongly disordered three-dimensional systems. A tight-binding formulation of strong-coupling superconductivity is combined, after configuration averaging, with the selfconsistent treatment of Anderson localization developed by Wollhardt and Wölfle. The Coulomb interaction becomes retarded via the joint local density of states, giving rise to an enhancement of the pseudopotential. Numerical T c results as a function of disorder are compared with another theoretical work and experimental values for some high- T c materials.