Twenty-six mandibular class III furcation defects were treated in 26 subjects using a regenerative therapy that included citric acid root conditioning, placement of freeze-dried decalcified bone allograft and coronally positioned flaps secured by crown-attached sutures. In addition to this therapy, expanded polytetrafluoroethylene (ePTFE) membranes were placed in 14 of the 26 defects. The effect of these therapies was evaluated after 52 to 60 weeks through a series of soft and hard tissue probing measurements including residual furcation classification. For both treatments, mean improvements were observed for furcal probing attachment levels, furcal bone levels, and defect volumes. However, only a few of these through-and-through defects had become closed as judged by a panel of 3 independent examiners. Four defects in each of the 2 treatment groups had changed from Class III to Class I/II or Class II/II evaluated with the soft tissue in place. One defect treated without membrane and 3 defects treated with membranes had changed from Class III to Class II as recorded after reflection of the soft tissues at re-entry. Little difference was observed between defects treated with and without membranes. Further studies with larger sample sizes and longer observation times are needed to fully evaluate these regenerative procedures and their potential for healing Class III furcation defects.