A catheter assembly including a catheter hub being connectable to a device for the infusion or withdrawal of fluids； a hollow extension tube connected at its distal end to the catheter hub, the extension tube connectable at its proximal end to a device for infusing fluid into the chamber within the catheter hub； a valve assembly disposed within the chamber of the catheter hub having a first valve member and a second valve member preventing the flow of fluid through the chamber to or from the proximal end of the catheter hub. A needle guard assembly is also provided.
