Abstract: A steam sterilization cycle having a conditioning stage, a sterilizing stage, a drying stage and an air admission stage which provides maximum removal of entrapped air from full or partial porous loads. The conditioning stage includes a plurality of pressure/vacuum pulses. The final vacuum pulses are deeper than the initial pulses. The sterilizing stage includes a diffusion dwell come-up which gradually increases the temperature and pressure of the chamber to the predetermined sterilization temperature by a sequence of pressure rises followed by pressure plateaus which permit substantially complete steam penetration of the load and substantial equalization of the actual load temperature and the temperature sensed by the sterilizer controls and substantially eliminates superheating the chamber. The cycle may also include a step for detecting and reacting to unacceptable levels of noncondensable gas present in the chamber during the sterilization stage.