Experimental results on void fraction and friction pressure drop in vapour-potassium flows in the high-vapour-quality region up to unity are presented. The experimental data obtained and the pertinent results of other authors are generalized, and empirical relationships are suggested to calculate void fraction and pressure drop in two-phase liquid metal flows for channels of various configurations and orientations. The relationships are valid within the range of vapour qualities from almost zero to unit. The experimental data prove the mass velocity to have no influence on the hydrodynamic characteristics within the range of the parameters investigated. It is found in the experiments with heat supply that friction pressure losses are smaller than those for adiabatic conditions. It is shown that this result is in good correspondence with the model of the effect of injection in a boundary layer on the value of shear stresses between cases.