Abstract: Methods and apparatus for liquid, gas, and gas plasma sterilization of items. The apparatus includes two chambers and a holder to connectorlessly secure a lumened instrument such that a first portion of the lumened instrument lies in the first chamber and a second portion of the instrument lies in the second chamber, a liquid medium contained within the two chambers, and pumping means for simultaneously increasing fluid pressure within the first chamber of said container while decreasing fluid pressure within the second chamber of the container in a reciprocating fashion. The pumping means displaces at least a total internal volume of the liquid medium through the lumen for a given highest volume of a lumened instrument during a stroke.