The determination of blood lead levels was included in a Swiss population survey on cardiovascular risk factors in 1984-1985; 931 men and 843 women aged 25 to 75 years participated in the study. Mean blood lead levels (+/- SD) were 0.63 +/- 0.27 mumole/liter for men and 0.44 +/- 0.19 mumole/liter for women, respectively, with a slight increase with age for both sexes. These values are below the maximum level recommended by the Commission of the European Community in 1977; 18 cases were found with blood lead higher than 1.5 mumole/liter and in six of these, a professional exposure was suspected. Smoking habits, drinking habits, and consumption of dairy products were selected as lifestyle descriptors and educational level, occupational category, and size of the community as sociodemographic indicators. Smoking and alcohol consumption show a direct association with blood lead, consuming dairy products an inverse one. Occupation and level of education are significantly related to blood lead only for men, blue-collar workers and less-educated men being more exposed. A higher blood lead level in cities was only found for women presumably because they stay at home more often than men and are therefore more sensitive to local exposure. In a multiple stepwise logistic regression, the lifestyle indicators showed a consistently stronger effect on blood lead than sociodemographic indicators. For men, smoking has an effect on blood lead for blue-collar workers much stronger than that for nonindustrial employees and may compound in some way the professional exposure to lead. This stresses the fact that interactions between lifestyle and environmental factors on blood lead are significant, complex, and need further investigation.