A dilator for sheathless access to a vessel of a patient, having a distal portion with a maximal outer diameter that extends from a distal end to a guidewire exit port and a proximal portion with a reduced profile that extends from the guidewire exit port to the proximal end and a lumen that extends between the distal end and the guidewire exit port. A first guidewire may be positioned within the vessel and the dilator advanced over the guidewire. A guide catheter may then be advanced over the dilator.