The present investigation was designed to evaluate the long-term effect of root-resective therapy in the treatment of furcation-involved molars. The patient sample included 72 patients, 21-62 years of age, who presented periodontal lesions in the posteriors segments of the mouth including furcation involvement of various degrees. After an initial examination, each patient was subjected to a series of full-mouth scaling and root planing. They were recalled 1-3 months later for a presurgical examination and subsequently underwent the corrective phase of therapy. During the surgical procedure, the furcation-involved teeth were subjected to root-resective therapy in conjunction with osseous recontouring and apically positioned flaps (test sites). A surgical procedure identical to the test procedure was performed in the non-furcation-involved teeth (control sites) with the exception of the root resection. At the completion of the active phase of treatment, 175 test and 175 control sites were available for the study. After a period of 6 months of healing and plaque control supervision following surgical procedures, the patients were recalled for a baseline examination. They were then enrolled in a maintenance program including professional tooth cleaning every 26 months. The patients were re-examined 3, 5 and 10 years post-operatively. The results of the assessments demonstrated that the survival rate, during the 10-year period of observation, reached 93% at test and 99% at control sites. The positive treatment outcome at the root-resected, furcation-involved teeth as well as at non-furcation-involved teeth was probably the consequence of the reestablishment of a tissue morphology favorable for oral hygiene and careful plaque control by the patients.