The treatment of furcation involvements is difficult because of the anatomic problems that interfere with the clinician's accessibility in treating the area and the patient's ability in maintaining adequate plaque control afterwards. The goal of traditional methods of treatment is to arrest the progression of bone loss; the rate of success with these methods has been poor, except for Grade I involvements. Advances in the last decade have resulted in the development of treatment techniques that attempt to reconstruct the lost periodontal structures. These techniques have greatly improved the prognosis of Grade II furcation involvement. The recommended technique combines the principles of guided tissue regeneration using polytetrafluoroethylene membranes with grafting with porous hydroxyapatite. The use of decalcified freeze-dried bone instead of hydroxyapatite also may be a successful method. Grade III and IV furcation involvements still have a poor long-term prognosis because predictable reconstructive techniques for their treatment have not been demonstrated. When possible, a root resection approach may be advisable.