The application of Response Surface Methodology (RSM) to the performance validation of a water cascade sterilizer is described. The methodology was successfully used to 1) identify the cold and hot zones within maximum load configurations through three dimensional thermal mapping, 2) demonstrate the consistency of consecutive sterilization cycles in companion sterilizers, and 3) set target sterilizing values (F0) to achieve a high statistical assurance that any location will be above a minimum F0 (sterility assurance) and below a maximum F0 (for stability considerations).