A sterilizer for medical instruments is compact and designed to be placed on a table top. The sterilizer provides includes a cavity for receiving a cassett e holding the instruments to be sterilized. A stream circuit provides steam to the cassette for sterilization, and the time required for sterilization is reduced by withdrawing air from the cassette by application of a vacuum. The cavity is evacuated at the same time as the cassette to prevent application of high stresses to the cassette during the vacuum-assisted withdrawal of air. The time for sterilization is further reduced by use of dual heat exchangers to reduce the volume removed from the cassette.
