Consumption of trans fatty acids (TFA) predicts higher risk of coronary heart disease, sudden death, and possibly diabetes mellitus. These associations are greater than would be predicted by effects of TFA on serum lipoproteins alone. Systemic inflammation and endothelial dysfunction may be involved in the pathogenesis of atherosclerosis, acute coronary syndromes, sudden death, insulin resistance, dyslipidemia, and heart failure. Evidence from both observational and experimental studies indicates that TFA are pro-inflammatory. Limited evidence suggests that pro-inflammatory effects may be stronger for trans isomers of linoleic acid (trans-C18:2) and oleic acid (trans-C18:1), rather than of palmitoleic acid (trans-C16:1), but further study of potential isomer-specific effects is needed. TFA also appear to induce endothelial dysfunction. The mechanisms underlying these effects are not well-established, but may involve TFA incorporation into endothelial cell, monocyte/macrophage, or adipocyte cell membranes (affecting membrane signaling pathway relating to inflammation) or ligand-dependent effects on peroxisome proliferator-activated receptor (PPAR) or retinoid X receptor (RXR) pathways. Activation of inflammatory responses and endothelial dysfunction may represent important mediating pathways between TFA consumption and risk of coronary heart disease, sudden death, and diabetes. Further study is indicated to define these effects of TFA and the implications of such effects for cardiovascular health.