This study compared the retentive ability of endodontic dowels cemented with a resin when the surfaces of the dowels were varied. Dowels of standardized material, shape, length, and diameter were cemented with an unfilled Bis-GMA resin. Four dowel surface configurations were tested: transverse serrated, crosshatched, threaded, and longitudinal spirals. The results indicated that the dowel surface design can significantly influence the retention of a resin-cemented dowel. Dowels with transverse serrations or crosshatching were retained better than dowels with longitudinal spirals or threads.