Over the last few years, there has been increasing interest in the relationship between industrially produced trans-fatty acids and cardiovascular disease. The Food and Drug Administration has ruled that processed foods must be labeled to indicate the total trans-fatty acid content. The label will not indicate the specific fatty acids, merely the total in the food. Some states and some countries have banned or limited the use of foods that contain these fatty acids without stipulating the individual fatty acids that are of concern. A general ban or limitation of trans-fatty acids in foods might not be in the best interest of the consumer because not all trans-fatty acids have deleterious effects on body function. Some have beneficial effects. This article will address this complex food issue with respect to knowledge about the different trans-fatty acids and their effects on metabolism.