Abstract: The body portion (A) of a small portable sterilizer has a face panel (46) against which a door (B) is selectively closed. The face panel defines an access opening for a sterilization chamber (10) which receives a cassette (C), an access opening for an anti-microbial concentrate chamber (20) which receives a powdered or other sterilant concentrate, and an outlet opening (50) from a microbe filter which filters microbes from incoming rinse water. The face plate and the door define fluid flow channels (48, 52) therebetween for selectively directing sterilant solutions and rinse solutions among the anti-microbial concentrate chamber, the sterilization chamber, and the microbial filter. The cassette is configured to assure that it is inserted into the sterilization chamber with a unique orientation such that its fluid inlet apertures (114) and outlet apertures (124) are at preselected locations.