[en] Experimental and theoretical study of angle resolved photoemission from the Al(100) surface is presented. Photoelectron spectra are calculated with an ab initio one-step theory of photoemission within the augmented plane wave formalism and are found to be in excellent agreement with the experiment. The lifetime of the (100) surface state and the photon energy dependence of the intensity of photoemission from the surface state are determined. The treatment of inelastic scattering by the optical potential within the one-step theory perfectly describes the surface sensitivity of the photoemission from Al(100) for energies up to 100 eV