Abstract: A carrier catheter (20) for the introduction and positioning or changing of one or more guidewires (GW1, GW2, GW3) or interventional devices in a vessel V in the body of a subject. The catheter (20) includes an elongated, thin flexible body (22) having a primary lumen (24) and ancillary lumens (26, 28). Each lumen has an opening at the proximal end and an opening (30, 32, 34) at the distal end to permit a guidewire or device to extend through and exit the lumen. The openings at the distal ends of the lumens are positioned so that the respective guidewires or interventional devices can exit the lumens at different locations along the distal end of the catheter. One introduction of the device allows the deployment of any combination of multiple guidewires and interventional devices. The catheter can be used for a rapid replacement of an indwelling catheter or rapid replacement of a dedicated guidewire.