All 55-yr-old citizens (n = 1012) of Oulu (a middle-sized Finnish town) were invited to a clinical examination; 780 agreed to participate. The associations of lifestyle with decayed tooth surfaces and the number of teeth were studied in the 533 dentate subjects. Measures of lifestyle included dietary habits, a smoking habit, alcohol consumption and physical activity. When the associations of dental caries with lifestyle, sex, dental health behavior, social class and number of teeth were studied by logistic regression analysis, lifestyle was shown to have an independent association with dental caries. Further analysis of the data showed that dental caries increased with a more negative lifestyle in every social class, but most significantly in the lowest. Number of teeth was not associated with lifestyle, but subjects with lower social status had fewer teeth than those with higher social status. The association of lifestyle with dental caries supports the idea that behavior in a broader sense should be taken into consideration in caries prevention.