Clinical responses of facial grade II molar furcations to closed (C) versus open (O) debridement were evaluated. 25 teeth were treated at baseline (BL) with scaling/root planning (S/RP) and evaluated at 4 months. 12 of the teeth were then treated with open flap debridement and the remaining teeth were treated with further S/RP. Clinical parameters of plaque, gingival inflammation, bleeding on probing, gingival fluid flow, pocket depth and probing attachment level were taken at BL, 4, 7, 10, 13 and 16 months. Pairwise differences were determined between visits and a t-test was applied to differences for C and O. For both treatment groups, the greatest changes in clinical parameters occurred from BL - 4 months. Plaque and gingival inflammation showed a gradual reduction from BL throughout the study for both groups. A reduction in pocket depth from BL - 16 months was noted in both groups (mid-furcal, C = 1.5 mm, O = 1.2 mm; root prominence, C = 1.02 mm, O = 0.84 mm)! There was a gain in probing attachment level in the midfurcal area for the C group (0.6 mm) while the O group lost (-0.46 mm). There were no statistically significant differences found for any clinical parameter between closed and open debridement. The presence of plaque and bleeding at a furcal site had not significant effect on treatment response.