Abstract: The hemostasis valve gasket for use in an introducer which is integrally formed from an elastomeric material so as to exhibit resiliency and which is designed to close about small diameter objects such as a guide wire and about larger diameter objects such as a working catheter or guide catheter to prevent air or blood leakage. The gasket includes a cylindrical base with a central bore therethrough and a hollow convex domed shaped member projecting therefrom. The hollow dome shaped member terminates in a concave section. The concave section of the dome shaped member has at least one arcuate slit formed in the external surface which extends inwardly toward the hollow chamber to form a central, self-sealing passage aligned with the central bore of the cylindrical base member.