The measurement of the two overall mass flow rates in a two-phase, gas-liquid pipeline is considered on the basis of dual pressure differential measurements for a combined contraction-frictional pipe type of flow meter. In particular the occurrence of compressible flow effects is established as an appropriate basis in such a metering arrangement for creating conditions where the two detected pressure differentials are not universally proportional. Under such conditions metering of the two flows in terms of the observed pressure differentials becomes practicable. The experiments generally conform with the predictions of a one-dimensional non-slip homogeneous flow model, and the correlation of wall friction factors with Reynolds number for gas-liquid two-phase pipe flow. The correlations of the velocity coefficients of abrupt and conical nozzles with void fraction have been obtained and incorporated in the analytical model for the flow meter. Whilst the practicability of such metering of two-phase flows is clearly demonstrated, application of the method would require careful calibration to allow for the influence of nozzle coefficient, pipe Reynolds number and void fraction upon the one-dimensional compressible flow equations through wall friction factor and interphase slip effects.