A method and apparatus for facilitating shoulder arthroplasty by providing a reference to establish version of the glenoid. In one form of the invention, a guide for positioning a guide pin to facilitate implantation of a glenoid prosthesis is provided. To properly position the guide pin, the guide is first oriented with respect to the scapula. A portion of the guide is positioned over the approximate center of the glenoid surface and another portion of the guide is positioned against the anterior surface of the scapula. After the guide is properly positioned, the guide pin is inserted through an aperture in the guide and anchored in the glenoid. Thereafter, the guide pin can serve as an alignment guide for other devices used to modify the glenoid surface. For example, a reamer having a cannulated central shaft can be placed over the guide pin and utilized to resurface the glenoid.