Calculations of the intensity of incoherent x-ray scattering (Iinc) from Si at small angles have been made using the full Waller-Hartree expression for comparison with the experimental results of Weinberg (1964). The agreement between calculation and experiment is poor for the entire angular range of the results (corresponding to q=(4π/λ)sinø/2 from 0.2 to 1.3 Å−1, where ø is the angle of scattering). Since Iincappears in the formulation of inelastic electron scattering by free atoms, it is pointed out that this formulation should be applied with caution to an interpretation of small-angle electron scattering by metal films.