Chronic Class II furcation lesions were created in four dogs. After 21 days, group 1 remained as a control, group 2 was treated with membranes and enamel matrix derivative (EMD), and group 3 received EMD alone. Healing in group 1 was characterized by a long junctional epithelium and discrete bone formation; group 2 showed reduced bone formation; and group 3 showed significant bone regeneration (area of new bone = 67.36% ± 3.93%; distance from furcation roof to bone crest = 0.57 ± 0.15 mm). The EMD led to significant regeneration of the furcation lesions, and the association with membranes was detrimental.