Purpose: To study risk-based preventive practice among Iranian dentists. Materials and Methods: A questionnaire survey was conducted at two annual dental meetings in 2004 and 2005 in Tehran. Using a five-point Likert scale, respondents indicated their level of agreement with taking preventive measures including oral hygiene, use of fluoride, diet and dental check-up for a high- and a low-risk (HR and LR, respectively) hypothetical patient case. Respondent's smoking and activity in smoking cessation were enquired about as well. Of 1033 responding dentists, 980 (64% men) were eligible for this study. Statistical evaluation was by the chi-square test and logistic regression. Results: The top four of the eight measures were instructions on tooth brushing and flossing, advice related to fluoridated toothpaste, and regular dental check-ups, with the choice 'fully agree' being more prevalent for the HR (74%-58%) than for the LR case (59%-41%). For the HR case, 45% of the respondents fully agreed with applying chair-side tooth cleaning, 41% with advice on diet modification, and 38% with advice on home-use of sodium fluoride mouthwash. Of all respondents, 76% were nonsmokers and 56% reported that they always recommend their smoking patients to quit. Female gender and activity in professional reading were associated with higher levels of agreement for applying preventive measures to the HR case. Non-smoking was the strongest explanatory factor (OR = 3.6, 95% CI = 2.6-5.1) of dentist's higher involvement in smoking cessation. Conclusion: Risk-based preventive dental care should be emphasised and applied in order to maximise efficient use of resources. Keywords: dentist's characteristics, preventive treatment, risk-based practice, smoking cessation