Abstract: A needleless connector allowing infusion and withdrawal of fluid in medical applications is disclosed. The injection site has a housing which contains a blunt cannula within it. An elastomeric pre-slit plunger is movably carried within the housing by the housing and said blunt cannula. Insertion of a connector moves the elastomeric pre-slit plunger from a first, occluding position deeper into the housing and over the blunt cannula to a second position, where the pre-slit portion of the plunger is penetrated by the blunt cannula. This opens a fluid passage from the inserted connector through the cannula to the opposite end of the housing, allowing fluid flow through the connector. Pressurized gas within the housing, or an elastically deformable member, or the two in combination, bias the elastomeric plunger back to its first position. As an inserted connector is removed, the fluid pathway through the injection site is re-sealed.