Lipoprotein(a) concentrations were measured by radial immunodiffusion in a cohort of 40-60 year males who had been classified by coronary angiography as CAD+ with 50% stenosis of one or more of the major coronary arteries or CAD- with no signs of coronary lesions. Sample odds ratios were calculated as a measure of association between serum Lp(a) values and the presence of coronary artery disease. An odds ratio of 2.706 (P less than 0.001) was derived for elevated (greater than or equal to 30 mg/dl) Lp(a) levels vs low (less than 5 mg/dl) Lp(a) levels indicating a strong association between the presence of coronary artery disease and elevated Lp(a) concentrations. This association was independent of the known risk factors smoking, hypertension and diabetes as well as the serum concentrations of total triglycerides, HDL-cholesterol, alpha-Lp-cholesterol and pre-beta-Lp-cholesterol. In contrast to these variables the association between Lp(a) and coronary artery disease was dependent upon the serum concentrations of LDL-cholesterol, beta-Lp-cholesterol and total cholesterol. At concentrations below the respective median for each variable, odds ratios of between 1.42 and 1.67 were calculated whereas at concentrations above the respective medians the odds ratios ranged from 4.50 to 6.33 (P less than 0.001). Our data, therefore, suggest that increasing LDL concentrations markedly increase the risk of coronary artery disease due to elevated Lp(a) levels.