Objective: Retrospective evaluation of success after tunnel preparation of class III furcation molars. Methods: In 41 patients (29 female, mean age 54.8±10.8 years) tunnel preparations were rendered to a total of 56 molars from 1992-2000. Before and 1 to 13 years after therapy examinations took place. A multilevel regression analysis was used to identify factors influencing the survival time of tunnel preparations: sex, jaw (maxilla/mandible), molar type (1st/2nd molar), smoking, participation in supportive periodontal therapy (SPT). Results: Six tunnel preparations were performed in the maxilla, 50 in the mandible. Forty tunnel preparations were done at 1st, 15 at 2nd, and 1 at 3rd molars. Eight tunnel preparations were lost during the observation period: 7 in the mandible. For the lost tunnel preparations a mean survival time of 40.8±18.6 months was observed. For those tunnel preparations that were still in function a mean survival time of 53.1±22.9 months was calculated. Multilevel regression analysis identified frequent SPT as positive (p = 0.08) and smoking (p = 0.08) as negative prognostic factors for tunnel survival. Conclusion: After an observation period of 50.7±22.6 months 48 of 56 tunnel preparations were still in function (86%). Schlagwörter: furcation involvement, resective therapie, long-term results