We have prospectively evaluated the risk of incident coronary events in association with serum total homocysteine in patients with preexisting chronic coronary heart disease. A nested case-control design was used. Total homocysteine concentration was measured in baseline fasting serum samples from patients with chronic coronary heart disease enrolled in the Bezafibrate Infarction Prevention Study (n = 3,090) who developed coronary events during 6.2 years of follow-up (n = 69). They were matched for age and gender with controls without subsequent cardiovascular events. Elevated homocysteine levels were associated with 2.5 times higher risk of subsequent coronary events and each 5 mumol/l increment was associated with a 25% higher risk.