BACKGROUND The objective of the study was to evaluate the degree of clustering of common lifestyle risk factors in a general adult population and to define subgroups with elevated clustering. METHODS Data on lifestyle risk factors (smoking, low vegetable and fruit consumption, excessive alcohol intake, and low physical activity), sociodemographics, and health perception were collected by questionnaire from 16,789 men and women aged 20 to 59. RESULTS About 20% of the subjects had at least three lifestyle risk factors. Prevalence of risk factors was higher among unemployed, low-educated subjects and those who had experienced health deterioration. All lifestyle risk factors showed significant clustering, except for low physical activity and excessive alcohol consumption. The strongest association was observed for alcohol and smoking (prevalence odds ratio (POR): 2.38; 95% confidence interval: 2.18-2.61). Clustering of smoking and alcohol consumption was strongest among the young subjects (POR: 3.78) and, although moderately, clustering of lifestyle risk factors was elevated in subjects who had experienced a deterioration in health. CONCLUSIONS These findings suggest that common lifestyle risk factors cluster among adult subjects. The tendency for risk factors to aggregate has important implications for health promotion. Information on high-risk groups will help in planning future preventive strategies.