Critical two-phase, steam - water flows have been measured in horizontal test sections with pipe diameters of 0.125 and 0.269 in. internal diameter (i.d.) over a range of qualities from 0.01 to 0.7, mass velocities from 500 to 4200 lb/sec-ft2, and critical pressures from 40 to 360 lb /in.2 absolute. The critical flow data and a theory for the critical flow phenomena have been discussed (1, 2). In this paper an analysis for the pressure drop data in the approach region to critical flow is presented. The flow mixture accelerates to critical flow at the end of the test sections, and thus the pressure drop data are for flow regimes in which both momentum and frictional losses are important. By utilizing the model developed for estimating critical discharge rates (1), two-phase friction factors were calculated from the experimental data. The friction factors obtained correlated well in terms of the two-phase quality and appear to be independent of flow rate, static pressure, and test geometry for the conditions examined.