A sterilizer for sterilizing medical instruments, the sterilizer having a pressurizable chamber having an opening communicating therewith. A door is provided for closing and sealing the opening to the chamber. A sterilant inlet and a sterilant outlet communicate with the chamber. A container holds medical instruments to be sterilized.The container is comprised of a tray and a lid dimensioned to rest on the tray. The tray and lid define an interior area for holding medical instruments. The tray has connection means for connecting the sterilant inlet to the interior area of the tray when the tray is inserted in the chamber, and the lid is movable from the tray when pressurized sterilant is introduced into the cavity.