The aim of this study was to examine the relation of lifestyle to the metabolic syndrome in Japanese male workers. The association of 6 lifestyle factors with the metabolic syndrome and the prevalence of the metabolic syndrome, as defined by the modified International Diabetes Federation criteria for Japanese people, were evaluated in 4941 men at a workplace participating in the annual health examination mandated by law; the subjects ranged in age from 36 to 60 years. The overall prevalence of the metabolic syndrome in the sample was 9.1%. The prevalence was the highest in subjects aged 46-50 years. The odds ratios (95% confidence interval) of the metabolic syndrome in current smokers and ex-smokers compared with non-smokers were 1.381 (1.088-1.752) (P=.008) and 1.812 (1.365-2.407) (P<.001), respectively. In contrast, no preventive effect of alcohol on the occurrence of the metabolic syndrome was noted.