The electrostatic charge activation model of conduction in discontinuous thin metal films is now widely accepted. There are, however, a number of discrepancies between theory and experiment and several aspects which are not well understood. The paper (a) briefly reviews the points of agreement between theory and experiment and surveys the reasons for rejection of other proposed theories, (b) considers the areas of disagreement between theory and experiment, and (c) discusses those aspects of the theory which are insufficiently well established to provide either confirmation or rejection of the theory. In particular, the tunneling parameters are considered in detail. It is decided that the theory, while not yet seriously disputed, does not account for all observations. More accurate determination of film structure is required before any final conclusion is possible.