Critical discharge of highly subcooled water through a cylindrical channel with a 0.78-mm inside diameter and 0.78 mm in length was experimentally studied. The range of the initial water subcooling was 76 to 200 K, and the initial water pressure was in the range 0.5 to 5.2 MPa. The measured critical mass fluxes were compared with three models appropriate for application to critical flow in small and short channels.The experimental results confirm the significant effect of pressure losses on critical discharge rates in small channels. They indicate, however, that the frictional pressure losses in cracks may be considerably larger than losses predicted by the widely used correlations for rough channels. It is shown that models and correlations based on isentropic homogeneous equilibrium flow in the channel accurately predict the critical flow data, provided that the liquid initial stagnation pressure is adequately corrected for the channel entrance pressure loss.