This report presents experimental results for the pressure drop across a restriction of annular geometry used in a typical pressurized water reactor steam generator. The pressure drops were obtained for air, water, and the corresponding two-phase mixtures. The loss coefficients associated with these pressure drops were experimentally determined and empirical relations correlating the results were developed. The tests were performed at atmospheric conditions (atmospheric temperature and pressure), and the two-phase flow mass velocity ranged from 236 to 711 1bm/s-ft2.