Abstract: An arrangement for sterilizing objects in which a quantity of liquid and one or more objects to be sterilized are introduced into a pouch formed of flexible sheet material at least partially transparent to microwave radiation whereupon the pouch is sealed to form a gas-tight assembly. The gas-tight assembly is situated in an inner rigid cavity of an enclosure which is at least partially formed of material that is substantially transparent to microwave radiation. The enclosure is irradiated with microwave radiation which passes into the cavity and then into the gas-tight pouch assembly situated therein to vaporize the liquid to produce an atmosphere of hot vapor under pressure in the pouch. The pouch expands under pressure until the sheet material of which it is formed presses against the rigid inner surfaces of the enclosure cavity.