Epidemiological studies have shown that loss of teeth is associated with increasing age. This was explained as the result of the action of microorganisms which, as components of dental plaque, destroyed the tooth by causing caries or periodontitis. Routine prevention programs therefore concentrated on removal of plaque, resulting in good oral hygiene. Despite good oral hygiene some individuals developed periodontitis. Studies have indicated that smoking may be a risk factor for this disease. This study was undertaken to determine whether or not smoking is also a risk factor for tooth loss. A total of 273 individuals were followed for 10 years, during which 93 individuals lost a total of 260 teeth. Younger individuals and especially males smoking more than 15 cigarettes a day were found to have the highest relative risk of losing teeth (4.55 and 3.18 respectively). In the younger age groups the proportional attributable risk was also highest; 78% for smokers smoking more than 15 cigarettes a day. The combination of a high plaque score and smoking was, together with age, the strongest predictor of tooth loss. The findings of this study suggest that smokers, especially those in the age group < 50 years, are a high risk group for tooth loss.