Emergency core cooling system performance analyses that demonstrate compliance with the 10CFR50.46 final acceptance criteria have been performed for the unique Westinghouse AP600 advanced pressurized water reactor. The AP600 plant features a low power density core, canned-motor reactor coolant pumps, passive safeguards systems, and an automatic depressurization system. It exhibits exceptional loss-of-coolant accident (LOCA) performance. A spectrum of small-break LOCA cases successfully depressurize while exhibiting no core uncovery; the maximum cladding temperature in each case is the initial steady-state value. The calculated peak cladding temperature for a design-basis large-break LOCA is only 1061 K at the design total peaking factor of 2.40.