Industry-generated trans-fatty acids (TFA) are detrimental to risk of CHD, but ruminant-originated TFA have been reported as neutral or equivocal. Therefore, the total TFA amount should not be the only factor considered when measuring the effects of TFA. In the present study, we addressed whether a version of the TFA index that unifies the effects of different TFA isomers into one equation could be used to reflect CHD risk probability (RP). The present cross-sectional study involved 2713 individuals divided into four groups that represented different pathological severities and potential risks of CHD: acute coronary syndrome (ACS, n 581); chronic coronary artery disease (CCAD, n 631); high-risk population (HRP, n 659); healthy volunteers (HV, n 842). A 10-year CHD RP was calculated. Meanwhile, the equation of the TFA index was derived using five TFA isomers (trans-16 : 1n-7, trans-16 : 1n-9, trans-18 : 1n-7, trans-18 : 1n-9 and trans-18 : 2n-6n-9), which were detected in the whole blood, serum and erythrocyte membranes of each subject. The TFA index and the 10-year CHD RP were compared by linear models. It was shown that only in the erythrocyte membrane, the TFA isomers were significantly different between the groups. In the ACS group, industry-generated TFA (trans-16 : 1n-9, trans-18 : 1n-9 and trans-18 : 2n-6n-9) were the highest, whereas ruminant-originated TFA (trans-16 : 1n-7 and trans-18 : 1n-7), which manifested an inverse relationship with CHD, were the lowest, and vice versa in the HV group. The TFA index decreased progressively from 7·12 to 5·06, 3·11 and 1·92 in the ACS, CCAD, HRP and HV groups, respectively. The erythrocyte membrane TFA index was positively associated with the 10-year CHD RP (R 2 0·9981) and manifested a strong linear correlation, which might reflect the true pathological severity of CHD.