The invention provides a method for replacing a first introducer, whose distal end is inside a vessel and whose proximal end is outside the skin of a patient, with a second introducer. The method comprises the steps of inserting a guide rod into the first introducer, removing the first introducer, passing the second introducer over the guide rod, and removing the guide rod. The guide rod to be used according to the method has preferably a flexible distal portion with a blunt distal end and a stiff proximal portion with a tapered proximal end.