This paper reports a theoretical study of the resistivity of solid and liquid sodium. It utilizes inelastic neutron scattering data to obtain the required information about the dynamics of the ions. The electron-phonon interaction is characterized by phase-shifts ηl, two of which are used as adjustable parameters. Although the calculation is believed to incorporate accurately many-body effects, umklapp processes, time-dependent effects, etc. agreement with experiment is disappointing. The calculated resistivity exceeds the experimentally measured values by a factor of the order of 2 at low temperatures, and above the melting point there are again discrepancies of this order. No convincing explanation of these disagreements has been found.