Experimental data on the loss of coolant from a pressurized-water test loop are presented. The test loop simulated the components of a full-sized reactor plant with an electrically heated test section, a pressurizer, a heat exchanger, and a circulating coolant pump. Leaks in the coolant system were simulated by rupture disks at various locations. The test results are compared with predictions using the FLASH computer program. The calculated system-pressure transients showed good agreement with the tests. The pressure differential across the test section exhibited an oscillatory behavior, as did the predictions in one of the three tests. Measured test-section temperatures showed a considerable variation from predictions; however, these temperature predictions represent an improvement over those using previous calculation methods.