A longitudinal study, extending over a period of 15 years, was carried out in a group of 102 patients who received 108 bridges made by the senior students at the Dental Faculty, University of Oslo, in 1967/68. The study included 343 abutment teeth, and the remaining teeth in the same jaw which received the restoration, 525 in all, served as control. The oral hygiene, gingival condition, pocket depth, caries on crowned teeth, location of crown margins and changes of alveolar bone level were recorded during the study. During the first 10 years, the patients received oral hygiene prophylaxis every 6 months. The mean age of the patients at the beginning of the study was 48 years. Of the original group of 102 patients, 88 attended the clinical examination after 5 years, 71 after 10 years, and 55 after 15 years. The amount of plaque did not differ between the crowned teeth and the control teeth during the observation period, while GI score 2 and 3 was more frequent in crowned teeth than in the control teeth during this period. This was mainly observed when the crown margins were located sub-gingivally. A slight increase in mean pocket depth was recorded in the crowned teeth while the mean pocket depth for the control teeth remained at the same level during the 15 years. Caries lesions were recorded in 3.3% of the abutment tooth surfaces at the 5th year, in 10.0% at the 10th year and in 12.0% at the 15th year examination. No statistical differences in bone loss could be detected between the control teeth and the crowned teeth.