At least one of first and second mold portions defines a mold cavity to receive molten plastic and form therefrom at least one molded part, and is movable relative to the other between (i) a closed position for sealing the mold cavity or cavities and molding at least one part therein, and (ii) an open position defining a fluid passageway between the mold portions and permitting the passage of a fluid sterilant therein. A fluid sterilant source is connectable in fluid communication with the fluid passageway for introducing the sterilant therein in the open position, contacting with the sterilant the surfaces of the first and second mold portions forming the fluid passageway and located adjacent to the at least one mold cavity, but not contacting an interior surface of a molded part within the mold cavity, to sterilize the exposed mold surfaces and thereby prevent contamination of the molded part.