A number of epidemiological studies have shown an association between beta-carotene and the risk of cardiovascular diseases, whereas only a few studies are available concerning the association of lycopene with the risk of coronary events, and no studies have been undertaken concerning lycopene and stroke. Thus, we tested the hypothesis that low serum levels of lycopene are associated with increased risk of acute coronary events and stroke in middle-aged men previously free of CHD and stroke. The subjects were 725 men aged 46-64 years examined in 1991-3 in the Kuopio Ischaemic Heart Disease Risk Factor Study. Forty-one men had either a fatal or a non-fatal acute coronary event or a stroke by December 1997. In a Cox' proportional hazard's model adjusting for examination years, age, systolic blood pressure and three nutritional factors (serum folate, beta-carotene and plasma vitamin C), men in the lowest quarter of serum lycopene levels (< or =0.07 micromol/l) had a 3.3-fold (95 % CI 1.7, 6.4, risk of acute coronary events or stroke compared with the others. Our study suggests that a low serum level of lycopene is associated with an increased risk of atherosclerotic vascular events in middle-aged men previously free of CHD and stroke.