A critical discussion is presented of the current status of the calculation of the dc electrical resistivity of simple metals. The general formalism, which has recently been given sound theoretical justification, shows that there are two elements to the calculation: (1) the dynamical structure factor, which describes the deviation of the ionic positions from perfect periodicity, and (2) the matrix elements of the screened electronion interaction. The first element can be obtained directly from experiment. The second element, the crux of the problem, has been calculated by a number of methods, including empirical means and the pseudopotential approach. These methods are shown to be inadequate for resistivity calculations because of the sensitivity of the electrical resistivity to the value of the matrix elements at large momentum transfers. It is demonstrated explicitly that the seemingly small errors present in pseudopotential calculations lead to errors as large as a factor of 2 in the electrical resistivity. © 1966 The American Physical Society.