A catheter holding device having longitudinally-extending walls defining an open-ended body with a main passage therethrough. At least a portion of the main passage is aligned with openings in forward and rear ends of the body. The portion of the walls adjacent the opening in the forward end of the body is adapted for receipt within a blood vessel or cavity. Another portion of the walls has a side opening allowing communication with the main passage. A side tube encompasses the side opening and extends from the body. Resilient material having a central passage therethrough is located within the side tube. The resilient material is designed to be compressed and grip a catheter which is passed through the material, into and through the main passage. A leading portion of the catheter projects beyond the forward end of the body. Clearance is left between at least one of the walls of the main passage and the catheter to allow simultaneous passage of liquids through both the main passage and the catheter. Thus, the catheter holding device is used for a number of dual functions, e.g., the simultaneous measurement of the central venous pressure and transfusion of liquids into the blood vessel.