The periodontal fenestration model was used in four young mongrel dogs to evaluate the ability of vertical root surface grooving to enhance and direct cell outgrowth and subsequent formation of new attachment at 2- and 6-week healing intervals. In each dog, three fenestration wounds were made on each side of the mandible. On the control side, the roots were planed to dentin, a barrier membrane was sutured over the wound, and the flaps were replaced over the membrane. The experimental side received three vertical grooves followed by membrane placement and flap replacement. Histologic and histometric analyses were performed to determine the amount of new bone, cementum, and ankylosis and maturation of wound healing. Grooved wounds demonstrated greater cementum and bone formation, primarily in the early wounds, in addition to a more mature attachment at 6 weeks. Grooving the root surface may enhance initial cell adhesion and proliferation, thereby accelerating new attachment formation.