Experimental data and an analysis of outsurge transients in a small pressurizer at constant electrical power input are discussed. The test section is a vertical cylinder that is connected at the bottom to a cylindrical horizontal section where the steam is produced by electric heaters. The range of the pressure is from 3 to 6 MPa. The fluid and outer wall temperatures are measured at several elevations, and the flashing rate and the fluid/ wall heat transfer are derived from the pressure and temperature time history data. The pressure transient is simulated by means of an extension of the Lu and Simpson prediction method.