The plasma trans-fatty acids of 47 patients with angiographically documented coronary artery disease were compared with those of 56 reference subjects using high-resolution capillary column gas-liquid chromatography to test the hypothesis that trans-fatty acid intake is a risk factor for cardiovascular disease. Individual and total trans-fatty acids were higher in patients than in reference subjects (1.38 vs 1.11% for total trans-fatty acids, p < 0.003; 0.40 vs 0.31% for palmitoleic acid trans, p < 0.001; and 0.28 vs 0.22% for linoleic acid trans, p < 0.007). High-density lipoprotein (HDL) cholesterol and HDL cholesterol/total cholesterol were negatively correlated (r = -0.29, p < 0.004; and r = -0.35, p < 0.001, respectively), whereas triglycerides, total cholesterol and low-density lipoprotein cholesterol were positively correlated (r = 0.47, p < 0.001; r = 0.22, p < 0.03; r = 0.20, p < 0.05, respectively) with palmitoleic acid trans. The correlations were similar and significant for linoleic acid trans, but less strong for total trans-fatty acids (which is more difficult to measure and has greater variability). Saturated and trans-fatty acids and total cholesterol are positively associated, whereas HDL/total cholesterol and polyunsaturated fatty acids are negatively associated with coronary artery disease. These results are consistent with the hypothesis that dietary trans-fatty acids are a cardiovascular risk factor.