A heart valve holder-inserter (21, 121) is designed to facilitate easy implantation of a mechanical heart valve prosthesis (23, 123). This holder-inserter, at its distal end, incorporates a pair of diametrically opposed guide members (47, 49, 81, 147, 149) which extend well beyond the leading edge of the prosthesis and which have exterior surfaces (53, 83, 153) of substantial dimension that are smoothly curved and proportioned so as to slowly spread the tissue annulus in order to facilitate easy entrance thereinto of the leading edge portion of the mechanical valve body.
