We discuss the renormalization-group formalism for calculating the electronic structure of surfaces. To illustrate operatively the features of the method, we consider the ideal and reconstructed Si (100)-(2 × 1) surface, because of the interest of this prototype cleavage face from an experimental and theoretical point of view. The renormalization-group method is shown to be computationally efficient and conceptually simple; it provides a convenient description of the electronic structure of surfaces, as well as other multilayer systems.