The cholesterol and choline-containing phospholipid fractions of high density lipoproteins (HDL) were determined in healthy males and in male patients with coronary heart disease (CHD) to ascertain which HDL parameter or combined parameters possess the greatest discriminative power. The free cholesterol fraction (HDL-fc) was found to be the most significant discriminator between controls and males with CHD, the mean levels (+/- SEM) being 6.6 (+/- 0.9) and 4.4 (+/- 0.6) mg/dl, respectively. Classification of CHD patients and controls using one-variable discriminant function analysis (DFA) yielded an error rate of 27% for plasma HDL-fc. Two-variable DFA using both the HDL esterified cholesterol levels and the HDL-fc levels of controls and patients reduced the error rate to 11%. The results obtained in this study indicate a possible role for HDL-fc as a predictor of CHD risk.