The lecture illustrates, by typical examples, the standard of mobility which can be achieved by present military vehicles. An outline is then given of the mobility improvements which might be obtained by the use of military ground-effect vehicles but, in the concluding section, emphasis is given to a number of generalised problems in the military operation of such vehicles which require detailed consideration before an adequate specification of ground-effect vehicles for military use is possible. The lecture deals only with overland vehicles —although capable of water crossing—which are designed specifically to exploit the ground-effect principle and whose capabilities for sustained airborne movement are limited to the ground cushion.