The purpose of this study was to histologically evaluate furcation defects in humans treated with an allograft-alloplast-tetracycline composite graft combined with an absorbable membrane for guided tissue regeneration (GTR). Three teeth with Class II furcation involvement on the buccal aspects were included in this study. A notch was placed in calculus during the procedure to serve as a reference point for histologic evaluation. The defects were then treated with an allograft- alloplast-tetracycline composite graft combined with an absorbable membrane for GTR. At 6 months postoperative, the teeth were extracted with conservative block sections and processed for histologic evaluation. Regeneration (new bone, cementum, and connective tissue attachment) coronal to a notch could be seen in one of the three defects treated. In the other two defects, a new connective tissue attachment was demonstrated (new connective tissue attachment into new cementum) in the notch placed in calculus. In this study, regeneration of a furcation defect in a human was documented with histology.