Previously, we demonstrated that the inductive properties of bone morphogenetic protein (BMP) highly depend on the nature of the carrier material used for implantation. In this paper, we show that administration of BMP incorporated in a fibrous collagen membrane can help to regenerate periodontal ligament and cementum both in cat canines and in monkey molars. The partially purified bovine BMP was combined with one or two layers of a fibrous collagen membrane. Although the single layer approach showed partial regeneration of periodontal defects, it also quite often led to ankylosis. The double layer technique in artificially prepared class III furcation defects in monkey molars gave favorable results. After 12 wk, not only the alveolar process but also the periodontal ligament and cementum had regenerated along the entire treated dentin surface. Collagen fibers were arranged more or less perpendicular to the surface of the new cementum. Ankylosis was not seen. It is concluded that the double-layer approach is superior to the single-layer technique in regenerating cementum.