A prosthesis delivery device having a proximal end and a distal end and comprising a sheath and a handle assembly, the handle assembly having a proximal end and a distal end and comprising: a main handle having a proximal end and a distal end, the sheath extending proximally of the main handle; a prosthesis release actuation mechanism disposed at least partially on the main handle and moveable relative to the main handle, wherein the prosthesis release actuation mechanism is rotatable about the main handle; a motion translating mechanism operatively connected to the prosthesis release actuation mechanism; and a second handle, which is disposed at least partially on the main handle and is longitudinally moveable relative thereto; wherein the motion translating mechanism is operatively connected to a prosthesis retention mechanism disposed at the proximal end of the delivery device, the prosthesis retention mechanism having a prosthesis capture condition and a prosthesis release condition; and wherein movement of the prosthesis release actuation mechanism causes movement of the motion translating mechanism thereby moving the prosthesis retention mechanism from the prosthesis capture condition to the prosthesis release condition; wherein the second handle has a first position on the main handle in which movement of the prosthesis release actuation mechanism is prevented and a second position on the main handle in which movement of the prosthesis release actuation mechanism is permitted; wherein longitudinal movement of the second handle relative to the main handle retracts the sheath in a distal direction and, as the second handle is moved from the first position on the main handle to the second position on the main handle, said sheath is retracted, thereby exposing at least a proximal end of the prosthesis; wherein the second handle, in said first position, covers the prosthesis release actuation mechanism so that the prosthesis release actuation mechanism is not visible and cannot be manipulated by the user; and wherein the prosthesis release actuation mechanism, in said second position, becomes exposed and is visible and accessible by the user. a main handle having a proximal end and a distal end, the sheath extending proximally of the main handle; a prosthesis release actuation mechanism disposed at least partially on the main handle and moveable relative to the main handle, wherein the prosthesis release actuation mechanism is rotatable about the main handle; a motion translating mechanism operatively connected to the prosthesis release actuation mechanism; and a second handle, which is disposed at least partially on the main handle and is longitudinally moveable relative thereto; wherein the motion translating mechanism is operatively connected to a prosthesis retention mechanism disposed at the proximal end of the delivery device, the prosthesis retention mechanism having a prosthesis capture condition and a prosthesis release condition; and wherein movement of the prosthesis release actuation mechanism causes movement of the motion translating mechanism thereby moving the prosthesis retention mechanism from the prosthesis capture condition to the prosthesis release condition; wherein the second handle has a first position on the main handle in which movement of the prosthesis release actuation mechanism is prevented and a second position on the main handle in which movement of the prosthesis release actuation mechanism is permitted; wherein longitudinal movement of the second handle relative to the main handle retracts the sheath in a distal direction and, as the second handle is moved from the first position on the main handle to the second position on the main handle, said sheath is retracted, thereby exposing at least a proximal end of the prosthesis; wherein the second handle, in said first position, covers the prosthesis release actuation mechanism so that the prosthesis release actuation mechanism is not visible and cannot be manipulated by the user; and wherein the prosthesis release actuation mechanism, in said second position, becomes exposed and is visible and accessible by the user.