Aim: To outline a protocol for orthodontic treatment of patients with advanced periodontal disease and to examine the short-term and long-term orthodontic and periodontal outcomes. Methods: Three typical cases followed long-term (51/2 to 14 years) are presented with evaluations of bone levels, root resorption, and orthodontic stability. A rigorous periodontal protocol is followed. Active disease must be in remission for at least 4 months prior to initiation of orthodontic treatment, and periodontal maintenance visits are continued at 3-month intervals. The goals of orthodontic treatment should consider the compromised periodontium and, when possible, avoid premolar extractions, heavy forces, and long treatment times. Slenderizing of anterior teeth, moderate expansion, and extraction of a mandibular incisor are useful techniques and avoid unrealistic demands on the reduced periodontium. All cases received permanent retention. Results: The three cases had favorable outcomes, with maintenance of bone levels following orthodontic treatment and long-term. The most important factors in the favorable outcomes were the periodontal maintenance by the patients and their periodontists and realistic orthodontic treatment plans. Conclusion: Orthodontic treatment was beneficial for the patients because dental alignment improved esthetics and allowed better instrumentation by the periodontist and ease of cleaning by the patient. Alignment also allowed for splinting by bonded wires, which minimized tooth mobility, and it placed abutments in favorable positions in the event that compromised teeth were lost in the future. World J Orthod 2001;2:127-141.