Total serum homocysteine and cholesterol levels were determined in 163 male patients with typical angina who were subjected to coronary angiography. The prevalence of homocysteinemia in coronary heart disease (CHD) was 41.9%. Serum homocysteine levels were significantly elevated (p less than 0.05) in patients with major occlusion in two or three coronary arteries. Furthermore, the prevalence of homocysteinemia correlated positively (p less than 0.05) with the number of coronary vessels that were occluded. The prevalence of hypercholesterolemia was 34.9%, but, in contrast to homocysteinemia, no graded strength of association with the number of stenotic coronary arteries could be demonstrated. The results suggest that homocysteinemia may contribute significantly to the development of coronary heart disease.