In a study of tooth extractions in general dental practices in Ontario, Canada, 165 dental practitioners provided information on 6134 patients attending during a reference week. Of these, 11.6 per cent of patients had one or more permanent teeth extracted. Periodontal disease was given as the reason for 35.9 per cent of these extractions and caries for 28.9 per cent. Analysis by tooth type showed that third molars were the most common tooth type extracted. However, there were differences in the types of teeth extracted by age. Posterior teeth were most frequently lost by the younger age groups and anterior teeth by older subjects. There were also differences in the reasons for the loss of different tooth types. A comparison of these results with those of a similar study in Scotland suggests that age and tooth type does not account for the excess of extractions due to periodontal disease in this Canadian population. Differences in practice patterns and attitudes towards the retention of teeth may be contributing factors.