Objective To investigate patients' views regarding dentists' smoking cessation advice. Design Survey questionnaire. Setting One hundred and thirty five dental practices in Sydney Australia. Subjects Two thousand, four hundred and fifty one dental patients. Results One thousand, one hundred and sixty pre-consultation questionnaires were obtained (RR=80%), 302 (26%) were self-reported smokers. From these, 623 post-consultation questionnaires were returned (RR = 54%). Most patients expected dentists to be interested in their smoking status (n = 847/1160, 73%, 95% CI: 70% to 76%) and to discuss smoking with them (n = 713/1160, 61%, 95% CI: 59% to 64%), however, smokers were significantly less likely to respond as such compared with non-smokers (P < 0.001). Smokers and non-smokers equally would not change dentist even if asked about their smoking status opportunistically (59% versus 62%) (OR = 0.91, 95% CI: 0.67 to 1.22). Less than one third of all smokers would try to quit if their dentist suggested they do so (n = 90/302, 30%, 95% CI: 25% to 35%). Smokers' recall of quit advice from their recent consultation was low (n = 22/124, 18%). Conclusions Smoking cessation advice by dentists is not self-evidently effective. These findings behove interventional research to ascertain efficacy of smoking cessation advice delivered by dentists before admonishing changes in routine clinical practice.Results from studies examining whether dentists are effective in assisting their patients who smoke to quit are inconclusive. In one randomised controlled trial, advice by dentists in Indianapolis (n = 54) achieved sustained patient quit rates of 7.7% enhanced by their use of nicotine gum. 1 However, three other well-designed studies failed to demonstrate significant results. 2-4 Specifically, a randomised controlled trial in Finland of a comprehensive intervention comprising annual inquiries of adolescents about their smoking, photographs of the harmful