The authors cross-sectionally investigated the extent to which coffee, tea, and alcohol consumption, physical activity, and smoking were associated with nonfasting total plasma homocysteine concentrations in a random sample of 3,025 Dutch adults aged 20--65 years from a population-based cohort examined in 1993--1996 (n = 19,066). The lifestyle factors most strongly associated with plasma total homocysteine level were smoking (positive), alcohol drinking (negative), and coffee consumption (positive). The smoking effect was most prominent in women, and the alcohol effect was most pronounced in men. Data indicated that independently of other lifestyle factors, age, and intake of folate and B vitamin supplements, a change in lifestyle could result in a 0.1- to 1.7-micromol/liter change in plasma total homocysteine level. The authors conclude that lifestyle changes could result in a public-health-relevant change in plasma total homocysteine concentrations.