The frequency dependent conductivity is considered within a memory function framework. In a detailed example of the use of this formalism the authors assume the ions to scatter the electrons by means of an energy independent pseudopotential, evaluating the memory function to second order in the pseudopotential, electron-electron interactions being in principle included exactly. The result so obtained for the conductivity, is shown to agree with a direct calculation in powers of the pseudopotential, corresponding to the summation of an infinite subset of terms in this series. In the limit of zero frequency, the Baym formula for the resistivity with a screened pseudopotential is regained, without assuming independent particle behaviour in any way.