A heart valve prostheses crimping apparatus and method for deducing the diameter of stents containing heart valve prosthesis. A medical prosthesis catheter loading apparatus, including a crimping assembly for reducing the diameter of a prosthesis； and a catheter clamp for holding a catheter adjacent to the prosthesis. Also disclosed is an apparatus for reducing the diameter of a medical prosthesis, including a base, a crimp head connectable to the base, and an actuation mechanism connected to the base and connectable to the crimp head to actuate the crimp head. Also disclosed is a method of loading a medical prosthesis into a catheter, including the steps of reducing the diameter of a prosthesis from its normal deployed state to a diameter less than that of the lumen of the catheter； holding a catheter adjacent to the reduced diameter prosthesis； and moving the prosthesis into the catheter lumen.
