Five hundred fifty-eight molars were treated with one of four types of periodontal therapy: coronal scaling (CS); root planing (RP); modified Widman surgery (MW); or flap with osseous resectional surgery (FO). This report presents the probing depth and probing attachment changes in the furcation region following therapy and two years of maintenance follow-up. All types of therapy were effective in reducing probing depths. FO was the most effective in reducing probing depth followed by MW, RP, and CS. Reduction in probing depth was primarily due to gingival recession. FO resulted in a loss of probing attachment in both a vertical and horizontal direction following therapy. Following two years of maintenance care, sites treated with FO continued to exhibit a mean net loss of vertical probing attachment. A mean net loss of horizontal probing attachment was present after two years of maintenance care, regardless of the treatment modality employed. Many more sites were initially removed during osseous resectional surgery to achieve treatment criteria than were initially removed from the other groups. FO treated teeth demonstrated a lesser percentage of furcation sites demonstrating clinically significant breakdown during the two years of maintenance care.