To evaluate the association of individual health habits with levels of cardiovascular risk factors such as serum cholesterol and blood pressure, data from a representative population sample of 860 men and 788 women, aged 25 to 64 years and residing in Western Switzerland, were analyzed cross-sectionally. The data had been collected during 1984/85 as a part of the WHO MONICA project, an international research project on the epidemiology of cardiovascular diseases. In age-adjusted analysis, a score of prudent diet was a reasonably strong inverse correlate of total cholesterol in men (p less than 0.001) but less so in women (p = 0.11); the diet score was unrelated to HDL cholesterol. In both genders, alcohol consumption was associated with elevated levels of systolic and diastolic blood pressure (men: both p less than 0.001; women: p = 0.05 and 0.01 respectively) and of HDL cholesterol (men and women: p less than 0.001). Coffee consumption was unrelated to either blood lipids or blood pressure. In both men and women, leisure-time exercise was a predictor of a low-risk lipid profile, i.e. a low total cholesterol/HDL ratio (both p less than 0.001). Better educated persons, especially women, revealed consistently lower levels of cardiovascular risk factors. The independent character of these lifestyle-risk factor-associations was largely confirmed in a multivariate analysis, with cigarette smoking emerging as another significant predictor of a deteriorated lipid profile, while education was not an independent determinant of biological risk factors. Lifestyle variables, including body mass index, explained 9 to 19% of variance in cardiovascular risk factors, with relative weight being the strongest of the predictors related to behaviour. Entering age and sex into the regression models enhanced the predictive power of the equations to 16 to 26% explained risk factor variance. We conclude from this population-based, cross-sectional study that personal health habits such as diet, exercise, alcohol consumption and smoking, as well as body weight are significantly and independently related to blood lipid and blood pressure levels; the apparent size of effect of these behavioural traits on biological risk factors for cardiovascular diseases was only modest, but it may nevertheless be relevant to prevention.