White blood cell (WBC) count is well known to be an independent risk marker for cardiovascular disease. The aim of this study is to examine the relationships of WBC counts to seven health practices including obesity, eating habits, smoking, alcohol intake, sleeping, physical activity, and perceived mental stress, and then clustering the relevant healthy practices. The subjects were 1,492 male and 316 female Japanese workers aged 40 yr and over in 2002. Each of seven health practices from a self-administered questionnaire was categorized as a 'healthy' or 'unhealthy' practice, and WBC counts from fasting blood samples were determined by automated particle counters. The means of age and WBC counts were 49.5 yr and 5,375 cells/microl in men, and 48.6 yr and 4,890 cells/microl in women, respectively. After multivariate adjustments for all health practices and age, the estimated WBC counts were significantly lower in normal weight subjects and never or former smokers (p<0.01). Age-adjusted WBC counts decreased significantly by 204.9+/-23.7 cells/microl (means+/-SE) and 117.6+/-53.2 cells/microl for each increase in one healthy practice (p<0.05), respectively, suggesting that cultivating healthier practices would lead to lower WBC counts. This study recommends modifying unhealthy practice one by one and maintaining healthy practices as an effective strategy for the prevention of atherosclerotic diseases, in addition, to quit smoking or abstain from heavy smoking especially in men is important to prevent the low-grade inflammation.