Cross-sectional and longitudinal studies have identified that persons wearing overdentures require regular care and maintenance of their dentures and their remaining dentition. This paper reports on a longitudinal study of the denture treatment needs of 284 dentures placed in 254 patients seen over a period of 12 years. At placement of the overdentures, baseline measurements and photographs were made by a single examiner. These measurements included evaluation of the restorations, abutment height above the gingival margin, periodontal probing depths, and oral hygiene. Denture status was evaluated by examining stability, retention, the integrity of the denture bases, and the relationship of the teeth in centric occlusion. Denture hygiene was also assessed. Based upon this examination, the subjects; denture treatment needs were determined. The majority of overdentures were well tolerated, and in general the patients were satisfied with their dentures. The most common denture treatment need was cle aning, followed by adjustment of the denture bases. Relaining was a more common problem in the mandibular arch than in the maxillae. The need for occlusal adjustment did not seem to be a problem after the fifth year, but this might have been because of replacement of worn teeth or dentures. The majority of denture repairs were necessitated before the sixth year. Patients who received immediate dentures did not have greater treatment needs. Looseness of the dentures was the primary complaint, followed by sore teeth and denture-bearing tissues. In spite of their complaints, the great majority of the patients were satisfied with their overdentures.a