The regeneration of periodontal supporting tissues lost as a result of disease could be accomplished by repopulating the exposed root surfaces with cells originating from periodontal ligament. Thus, we aimed to assess the seeding of cells derived from regenerated periodontal ligament (RPL) to promote the regeneration in artificial furcation defects of a dog. The fibroblast-like cells were obtained by incubating the explants of RPL tissue taken under a teflon (E-PTFE) membrane. Class II furcation defects were induced on the second and fourth mandibular premolars. Control defects were also included on the contralateral side. A suspension of the fourth passage cells (2 x 10(5) cells) in 0.5 mL of autologous blood coagulum was placed over each furcation area. The healing was histomorphometrically evaluated at the 42nd day postoperatively and expressed as percentage. The healing by new connective tissue attachment with cementum formation was found 75% in the cell-seeding defects whereas, it was 71% in controls. Bone formation was found to fill 51% of furcation defects; however, it was 35% of the defects in the control sites. In this pilot study, we suggested that regeneration of furcation defects by cell-seeding technique may be useful, but further studies are needed to determine the outcome of the procedure.