Abstract: A catheter gard unit is disclosed herein which includes a flexible tapered introduction guide. The distal end of the tapered introduction guide, in a sheath procedure, is placed over a guide wire and into a sheath, both of which have been pre-placed within a patient's body. In a sheathless procedure, the distal end of the tapered introduction guide is placed adjacent the skin of the patient and over the pre-placed guide wire. The gard unit comprises a body with a passageway therethrough for the passage of the catheter tube. A resilient slidable seal is mounted upon the tapered introduction guide of the gard unit. The slidable seal is adapted to slid over and seal the connection between the introduction guide, through which the catheter is placed, and a hemostasis valve of the sheath, after insertion of the sheath into the patient's body and thereby form a liquid seal between the introduction guide and the sheath.