While substantial proportions of the population of Ontario, Canada continue to have teeth extracted, little is known about the reasons for this loss. In this survey of Ontario general dental practitioners, 128 dentists provided information on 6143 patients they saw during a reference week. Approximately one-in-seven of these patients had or were going to have one or more extractions as part of their current course of treatment. The mean number of extractions for patients having at least one tooth taken out was 2.3 (SD = 2.5). Emergency patients were more likely than regular patients to have at least one extraction but, on average, had fewer teeth taken out. Orthodontic considerations were the main reason for tooth loss in childhood, caries continued to be an important cause of tooth loss at all ages and periodontal disease accounted for more teeth lost after 40 years of age than caries. This study differs from almost all others in finding that, overall, more permanent teeth were extracted because of periodontal disease than because of caries. The former accounted for 35.9% of teeth lost and the latter for 28.9%. While this may be due to methodological differences between this and other studies, it is consistent with epidemiological data on periodontal disease in the Ontario population and data showing that Ontarians receive little in the way of periodontal care.